Engineering Surveys for Industry [1st ed.] 9783030483081, 9783030483098

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Alojz Kopáčik Ján Erdélyi Peter Kyrinovič

Engineering Surveys for Industry

Engineering Surveys for Industry

Alojz Kopáčik • Ján Erdélyi • Peter Kyrinovič

Engineering Surveys for Industry

Alojz Kopáčik Department of Surveying Slovak University of Technology in Bratislava Bratislava, Slovakia

Ján Erdélyi Department of Surveying Slovak University of Technology in Bratislava Bratislava, Slovakia

Peter Kyrinovič Department of Surveying Slovak University of Technology in Bratislava Bratislava, Slovakia

ISBN 978-3-030-48308-1    ISBN 978-3-030-48309-8 (eBook) https://doi.org/10.1007/978-3-030-48309-8 © Springer Nature Switzerland AG 2020 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Geodetic measurements are significantly affected by special conditions, which are typical for the industrial surrounding. These are different from the conditions under which the geodetic measurements are generally accomplished. In an industrial environment, many phenomena are dominant, which leads to a systematic impact on measuring instrumentation and it influences the measured values too. This should be taken into account by measurement planning as well as the data processing made in the industry. The knowledge of these phenomena and their effect on the measurement enables us to minimize their influence on the measurement results. This topic is discussed in the book at the beginning, to present these specific conditions to the reader. This part ends with safety information and regulations, which are very important for surveyors working in an industrial environment. Parallel to the progress in industrial production in the last years, resulting in automatization of many processes, the requirements on their quality increase, too. The quality assurance of any manufacturing is based on the ability to repeat series of steps (activities, actions) with the same physical and geometric parameters (robot implementation in production, automated production, etc.). In most cases, it is required to ensure this in the long term. Verification of these parameters is based on control measurements, which should document the rightness of the adjustment of operations, the technology used, and their geometric correctness during the whole production process. Fulfillment of these conditions enables to fulfill the production quality requirements given for the final product. Most of these control measurements use principles, which are known in surveying and use them in their processes. The book brings information about typical quality requirements in the industry, the methodology generally used, principles of high precision measuring systems, and their possible application. It also discusses the quality of measurements’ results. Geodetic measurements are generally based on a network of reference points. According to the high quality requirements in the industry, geodetic networks are built under specific conditions and increased accuracy requirements. In the case of setting-out and control of equipment, these requirements are higher, resulting in the creation of micro-networks, which are special networks of very high accuracy. The book deals with the methodology of their design, measurement, and data v

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Preface

processing. Subsequently, the principle, application, and usage of both the Cartesian and polar coordinate measuring systems as basic tools of the quality control in the industry production are discussed. Terrestrial laser scanning technology, which is used for creating documentation of industry objects and equipment as well as for in situ documentation of accidents, deformations, or data collection for factory maps and information systems, is also discussed in the book. The last chapters are devoted to the measurement of cranes, rotary kilns, and special objects of nuclear power plants. The book can be helpful for teachers, students, as well as practitioners (surveyors) who deal with these kinds of measurements. Chapters, which discuss the topic of coordinate measuring systems, the quality of industrial measurements, etc., could be helpful for quality managers in productions. Presentation of geodetic methods, their principles, and limitations as well as their possible application for the industry could support the cooperation between surveyors and experts working in manufacturing. Mechanical engineers or designers of equipment or its parts could learn from the book how to measure the geometry or how to create a 3D model of the developed elements with high accuracy. Information according to testing and calibration of measuring systems can be very valuable for the reader too. The book is in accordance with the current development in this scientific field, in geodesy and cartography, or related sciences. It also provides up-to-date information in accordance with current legislation and technical regulation (at the time of its publishing). The book informs about the present trends in this field, specifically in automatized measuring. The topic is being discussed at the level of current knowledge of industry and technological basis so that it reflects the usual effective technological processes in practice. Authors would like to thank to reviewers and colleagues for the patience, cooperative spirit, and for finding all the errors. We would also like to thank Richard Honti for drawing the pictures. Without their help, this book would not be published. Bratislava, Slovakia   December 2019

Alojz Kopáčik Ján Erdélyi Peter Kyrinovič

Contents

1 Specific Conditions of Geodetic Measurements in Industry����������������    1 1.1 Motivation ����������������������������������������������������������������������������������������    1 1.2 Environmental Conditions and Their Impact on Measurements������    2 1.3 Safety Regulations of Industry Measurements ��������������������������������    8 1.4 Accuracy Requirements of Industry Measurement��������������������������   10 2 Quality of Industrial Measurements������������������������������������������������������   13 2.1 Definitions and Terminology������������������������������������������������������������   13 2.2 Quality Evaluation of Industrial Measurements ������������������������������   18 2.3 Metrology of Industry Measurement������������������������������������������������   20 2.4 Geodetic Equipment and Instrument Testing and Evaluation����������   24 References��������������������������������������������������������������������������������������������������   27 3 Maps and Information Systems of Industrial Plants����������������������������   29 3.1 Large-Scale Base Maps��������������������������������������������������������������������   29 3.2 Factory Base Map Design and Creation ������������������������������������������   30 3.3 Factory Base Map Updating ������������������������������������������������������������   37 3.4 Information Systems of Industrial Plants������������������������������������������   38 4 Geodetic Networks of Industrial Equipment and Plants ��������������������   43 4.1 Local Geodetic Networks of Industrial Plants����������������������������������   43 4.2 Geodetic Micro-Networks of Industrial Plants ��������������������������������   47 4.3 Measurement of Angles in Micro-Networks������������������������������������   50 4.4 Measurement of Distances in Micro-Networks��������������������������������   51 4.5 Design of the Accuracy of Micro-Networks ������������������������������������   55 References��������������������������������������������������������������������������������������������������   58 5 Special Methods for Measurement of Industrial Equipment��������������   59 5.1 Categorization of Methods����������������������������������������������������������������   59 5.2 Methods of Direct Measurement������������������������������������������������������   61 5.3 Methods of Non-direct Measurement ����������������������������������������������   67 5.4 Measurement Systems for Precise Tilt Measurement����������������������   70 References��������������������������������������������������������������������������������������������������   81 vii

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6 Terrestrial Laser Scanning Systems ������������������������������������������������������   83 6.1 Functional Principle of TLS��������������������������������������������������������������   83 6.1.1 Distance Measurement����������������������������������������������������������   86 6.1.2 Projection Mechanisms for Laser Beam Deflection ������������   89 6.1.3 Categorization of Laser Scanners ����������������������������������������   91 6.2 Measurement Using Terrestrial Laser Scanners��������������������������������   93 6.2.1 Preparation for Scanning������������������������������������������������������   93 6.2.2 Scanning��������������������������������������������������������������������������������   95 6.3 Processing of Data Obtained by TLS������������������������������������������������   97 6.3.1 Point Clouds Adjustment������������������������������������������������������   98 6.3.2 Creation of 3D Models���������������������������������������������������������  102 6.4 Accuracy and Calibration of Terrestrial Laser Scanners������������������  106 6.4.1 Source of Errors and their Mathematical Models ����������������  106 6.4.2 Calibration of Terrestrial Laser Scanners�����������������������������  109 6.4.3 Laboratory Tests of Laser Scanners��������������������������������������  111 6.4.4 Field Tests of Terrestrial Laser Scanners������������������������������  115 References��������������������������������������������������������������������������������������������������  118 7 Coordinate Measuring Systems and Machines ������������������������������������  121 7.1 Principle of Coordinate Measuring Machines����������������������������������  121 7.2 Categorization of CMMs������������������������������������������������������������������  122 7.3 Polar CMMs��������������������������������������������������������������������������������������  125 7.4 Orthogonal CMMs����������������������������������������������������������������������������  128 7.5 Probing Systems of CMMs��������������������������������������������������������������  133 7.6 Accuracy and Testing of CMMs ������������������������������������������������������  136 References��������������������������������������������������������������������������������������������������  141 8 Setting-Out and Measurement of Cranes and Crane Runways����������  143 8.1 Basic Terms and Definitions ������������������������������������������������������������  143 8.2 Classification of Cranes��������������������������������������������������������������������  145 8.3 Crane and Crane Runway Parameters����������������������������������������������  148 8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways��������������������������������������������������������������������������������������������  150 8.5 Data Processing and Analysis ����������������������������������������������������������  162 8.6 Automated Measurement of Rails����������������������������������������������������  170 References��������������������������������������������������������������������������������������������������  178 9 Setting-Out and Control of Rotary Kilns����������������������������������������������  179 9.1 Conditions of the Correct Rotary Kiln Operation����������������������������  179 9.2 Geodetic Works Related to Rotary Kiln Assembly��������������������������  182 9.3 Geodetic Methods of Rotary Kiln Control and Rectification ����������  186 9.4 Calculation of Rectification Parameters��������������������������������������������  188 Reference ��������������������������������������������������������������������������������������������������  195

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10 Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities������������������������������������������������������������������������������������  197 10.1 Motivation ��������������������������������������������������������������������������������������  197 10.2 Assessment and Evaluation of the Locality for Nuclear Power Plant Construction���������������������������������������������������������������  199 10.3 Main Objects of a Nuclear Power Plant������������������������������������������  201 10.4 Geodetic Measurements During Nuclear Power Plant Construction��������������������������������������������������������������������������  203 10.5 Geodetic Measurements During Nuclear Power Plant Operation ������������������������������������������������������������������������������  207 10.6 Institutions and Standards Supporting the Safe Operation of the Nuclear Power Plant ������������������������������������������������������������  212 References��������������������������������������������������������������������������������������������������  213

List of Abbreviations

A/D AM ARTIS BIPM

Analog/digital (converter) Amplitude modulated (signal) Advanced Rail Track Inspection System (crane rail measuring system) Bureau of Weights and Measures (Bureau International des Poids et Mesures) CASCO ISO Committee for Conformity Assessment CCD Charge-coupled device (optical sensor) CIPM International Committee for Weights and Measures (Comité International des Poids et Mesures) CIML International Committee of Legal Metrology CNC Computer numerical control (machine, instrument) CMAA Crane Manufacturer Association of America CMI Coordinate Measuring Instrument CMM Coordinate measuring machine CMOS Complementary metal–oxide–semiconductor (metal–oxide–semiconductor field-effect transistor type) CMS Coordinate measuring systems CSG Constructive Solid Geometry EDM Electro-optical distance meters EN European Standards EXCn Execution Classes (defined by European standards for steel structures) FM Frequency modulated (signal) FEM European Federation of Material Handling GNSS Global Navigation Satelite Systems GD&T Geometric dimensioning and tolerancing GPS Geometrical product specifications HMI Hoist Manufacturers Institute IAEA International Atomic Energy Agency IEC International Electrotechnical Commission IERICS Independent Engineering Review of I&C Systems ILAC International Laboratory Accreditation Cooperation xi

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IMU IS ISO ITG LED LMS

List of Abbreviations

Inertial measuring unit Information system International Organization for Standardization, International standards International Tolerance Grades Light-emitting diode Laser measuring system (Demag Crane & Components crane rail measuring system) LOD Level of detail LSM Least squares method NMI National Metrology Institute NURBS Non-Uniform Rational B-Spline (surface) OIML International Organization of Legal Metrology PLS Profile laser scanners PLiM Plant Life Management (program for management of nuclear power plants) RTK Real-time Kinematic (GNSS method) SC Sub Committee (ISO) SI International System of Units SI (Systéme International d'Unités) VIM3 International Vocabulary of Metrology (3rd edition) TC Technical Committee (ISO) TLS Terrestrial laser scanning UAV Unmanned aerial vehicle (known as a drone) US NRC US Nuclear Regulatory Commission WANO World Association of Nuclear Operators

About the Authors

Alojz Kopáčik,  Ph.D., is a Professor of Geodesy and Cartography and the Head of the Department of Surveying at the Slovak University of Technology in Bratislava. He has been lecturing on Engineering Surveying, Underground Surveying, and Legislation in Surveying since 2000. His main research areas are Engineering Surveying, Automation of Measuring Systems, and Deformation Analysis. He is the author and co-author of 6 books, editor of 12 proceedings, the main investigator of many research and commercial projects, member of the German Geodetic Commission of the Bavarian Academy of Sciences, the FIG, TCs in the field of standardization, of examination commissions at many universities, and the Chamber of surveyors and cartographers in Slovakia, and is a licensed surveyor. Ján Erdélyi,  Ph.D., is an Associate Professor at the Department of Surveying at the Slovak University of Technology in Bratislava. He has been lecturing on Engineering Surveying and Engineering Surveys for Industry since 2009. He worked on the Habilitation on Use of Terrestrial Laser Scanning in Construction and Industry in 2018 at the STU in Bratislava, and he performs research activities in the field of TLS, Deformation Analysis, and Building Information Modeling. He is a co-investigator of many research and commercial projects aimed at different fields of engineering surveying. Peter Kyrinovič,  Ph.D., is an Associate Professor at the Department of Surveying at the Slovak University of Technology in Bratislava. He has been lecturing on Engineering Surveying and Surveying since 1999. He worked on Habilitation on Measuring Systems for Geodetic Monitoring of Building Structures in 2018 at the STU in Bratislava. His main research areas are Engineering Surveying, Automation of Measuring Systems, and Deformation Analysis. He is the author of several projects in these fields.

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Chapter 1

Specific Conditions of Geodetic Measurements in Industry

Measurements done in the industry environment are very intensely influenced by specific conditions, which characterize the environment in industrial plants or enterprises. There are effects, which have a large impact on the measurement process, measured values, and on the measurement instruments systematically, which are very important to take into consideration. The chapter brings information about the specific conditions of the industrial environment, discusses this from the point of view of the surveyors, the methods, and instruments which are generally used. In the second part of the chapter is included information about the safety conditions and rules, the knowledge of which is very important for the surveyors. The last part of the chapter is devoted to the accuracy requirements of industrial measurements, their classification, and fulfillment.

1.1  Motivation With the development of machine production and its automatization grow also requirements on quality. Quality assurance of any activity (including production) is based on a series of repeated steps (actions) at the same physical and geometric parameters. Control of the parameters is usually based on controlling measurement results, which prove the accuracy and rightness of process settings and of equipment, their measurement stability during the production process, as well as the fulfillment of qualitative parameters (requirements) formulated for the final production (product). Most of these control measurements use known principles in geodesy, and it is based on geodetic methods and procedures. Geodetic measurements done in the industry environment are very intensely influenced by specific conditions, which characterize the environment in industrial plants or enterprises. These very largely differ from the conditions, at which usually the geodetic measurements are done. There are effects, which have a large impact on the measurement process, measured values, and on the measurement instruments © Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_1

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1  Specific Conditions of Geodetic Measurements in Industry

systematically, which are very important to take into consideration while processing, not only the measurement itself but also the results. However, patterns of the effects and their recognition enable to eliminate their impact on the measurement results or, to be more precise, to eliminate the impact to an acceptable extent. At production quality control, we usually meet with a wider scale of parameters, than in regular geodesy practice. To parameters such as directness, horizontal line, verticality, or rectangularity, we need to add others, connected with the geometric shape and with their relative position in the space (deviations from the plane, cylinder, sphere or other spherical surfaces, etc.). Increased accuracy requirements, the systematic impact of the environment on the measured parameters, the equipment, and specific requirements, generate the necessity of constant development and precision of measurement methods and processes, and they require the use of nontraditional theoretical solutions by measurement results evaluation. The necessity of new measurement processes development to control geometric parameters of machine technological equipment and to control products is emphasized also by the current development of modern production technologies and methods in the machine industry.

1.2  E  nvironmental Conditions and Their Impact on Measurements The environment of the industry is completely different from the environment, where geodetic measurements are regularly done. The difference between measurements in nature compared to the industry environment, plants, premises, or enterprises lies predominantly in: • Different properties of the environment, where measurements are done • Dimensions of the measured object (they are usually smaller than outdoors) • Required accuracy (usually one order higher than measurements done in building constructions) • Work safety requirements (the safety requirements are more strict) Most of the geodetic measurement done in an industry environment is usually performed inside the building; in working rooms, plant halls, and in premises, which are directly connected to operational processes. Insufficient light conditions, such as duskiness or darkness, make the measurement more difficult. Premises inside buildings have usually specific climate conditions determined by the type of production. Often, when measuring, there can be a different temperature in different areas. These temperature changes are caused not only by the heating and ventilation system but also because there are different sources of heating in these spaces, too. Differences in temperature measured in different spots cause refraction when measuring angles, distances, and verticals.

1.2  Environmental Conditions and Their Impact on Measurements

3

Heated spaces are usually dry, whereas other spaces (predominantly underground spaces) are damp, which causes different humidity of the surrounding. Passages between different parts of operations are usually open spaces, which causes air draught. This can be unnoticeable for a measuring person; however, it deprives the results of optical measurement and some parts of mechanical measurement very strongly, too (e.g., at mechanical setting-out of verticals). Vibrations caused by the operation process of technological parts cause vibration of the measuring equipment, which results in less accurate measurement results. The vibration caused by the operation of mechanisms (engines) can have certain consequences in measurements. The activity of the measuring group can be even more difficult because of the high level of noise, which is noticeable mainly in close proximity of engine machinery, such as turbogenerators, steam generators, etc. These phenomena do not have an impact not only on measurement itself in this environment but also on activity of the whole measuring group. Different conditions cause measurement errors, which are of a different character in a certain time and maybe noticeable only after repeated measuring, done at different conditions. Repeated measurement in engineering surveying is not always possible because of limited operation conditions (limited time appointed for measuring given by operational shutdown or by the operational schedule). In such cases, it is necessary to use those measurement proceedings, which limit most of the impacts of the environment on the measurement, and results, too. When deciding for a suitable proceeding, it is necessary to base this decision on a true knowledge of all patterns of phenomena. It is necessary to find the right time for measuring or time when we will be able to minimalize the impact of these phenomena. Light conditions in industry spaces are very different, too. They can vary from bright light to dim light or full darkness. The measuring person can face such light condition changes several times per one measuring. These changes can come very quickly (e.g., when entering to another room or passing from interior to exterior.). When working inside the building during the operation of machines or equipment, it is necessary to ensure the lighting of the measuring instruments, targets, reflective prisms, and measuring rods (staff). The most modern (electronic) geodetic instruments are equipped with lighting for night measuring. A problem can appear when using optical instruments, which do not have the lighting as a built-in part given by the producer; it is necessary to order it separately. In most cases, instruments do not have such lighting and therefore it is necessary to use additional external lighting sources (torches or other LED flashes and lights). At these conditions, the measuring group needs an extra person, who lights the targets or the staffs. Good lighting needs to ensure the right setting of the bull’s eye or tubular level, correct reading on the well-lit measuring rod and has to ensure correct reading on the optical micrometer. To light staff, targets, or reflective prisms, we usually use torches or reflectors with accumulators. These, however, can light only a part of the staff, which is insufficient for reading with digital levels (usually, we need to enlight the staff for at least 0.3 m to 0.5 m). There had been developed some appliances based on LED strips, which can light up the whole staff, or its part sufficient to measure with digital levels (Fig. 1.1). It is necessary to light the staff so that the light

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1  Specific Conditions of Geodetic Measurements in Industry

Fig. 1.1  Staff lighting using LED strips

reflected from the staff does not reflect light on the measuring person and does not disable the correct targeting of the staff. Refraction is caused by different temperatures of air layers, through which goes the line of sight. In consequence of different temperatures of air layers, the air density changes and as a result of this, the air refractive index changes in individual air layers. Therefore, the line of sight does not go through the layers in a straight line but curves into an arch, which is usually replaced by a circular line with a very large radius. Refraction causes errors in measuring horizontal angles and distances (horizontal or lateral refraction), in measuring vertical angles, in measuring elevation by leveling, and in setting-out verticals (plumb lines) – vertical refraction. Lateral refraction emerges by measuring horizontal angles in cases when the line of sight is close to objects, which are heated either with sunbeams (walls, columns, material stockpiles) or by other heat sources (boilers, heat exchangers, steam pipes, heat pipes, engines). The impact of the side refraction can be decreased by offsetting of the targeting from the heated (cooled) object by minimum 0.5 m. However, by measuring in industry, it is not always possible. Lateral refraction has an intensive impact on measuring parallactic angles at measured distances with the base rod. If the line of sight goes on one of the targets of base rod very close to an object, which is a heat source or is heated, the parallactic angle δ changes by an error from refraction Δδ and the measured distance will be shorter or longer (Fig. 1.2). Elevation determined by the leveling method usually is impacted by so-called differential leveling refraction. It has an impact predominantly when passing between spaces with different temperatures (e.g., from the exterior to interior). In these spaces, the temperature gradients can be very different, which can cause the curving of the measuring line of backsight and foresight (Fig. 1.3). The differential refraction can be calculated from the difference of refraction impacts on the line of sight in a backward and forward direction, according to the relation

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1.2  Environmental Conditions and Their Impact on Measurements

Fig. 1.2  Impact of the lateral refraction on the angles and distances measurements in industry

Fig. 1.3  Impact of the differential refraction on the measured elevation



∆h = ∆h2 − ∆h1 ,

(1.1)

where Δh1 is the error in assessing the staff reading caused by refraction in backsight. Δh2 is the error in assessing the staff reading caused by refraction foresight. Differential refraction is a dangerous systematic error, which is often not “noticed” and does not occur either in measuring forward and backward nor in enclosures of leveling lines if the repeated measurements were done at same conditions. Usually, it occurs at places of passing from exterior to interior. As a

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1  Specific Conditions of Geodetic Measurements in Industry

Fig. 1.4  Correct position of leveling instrument and leveling staff when passing between spaces with different temperatures

consequence, we face a heavy shortening of the line of sight in these spaces. Therefore, we always put into the passing area the leveling staff, never the leveling instrument (Fig. 1.4). The temperature impact of the environment can be noticed mainly when measuring distances with measures (e.g., steel tape). The most frequent error is omitting or incorrect assessment of the temperature of the measure, which is changing its temperature with the environment, too. Deviation of the measure’s temperature or the equipment which is measured, from the nominal value of the temperature is usually seen as a systematic error in measurement results, whereas temperature changes during measurement cause errors, which are of a random character. Error caused by the impact of the environment temperature grows with the measured distance, and when the measuring objects are larger than 100 m, this error is a crucial part of all errors of measuring. The systematic part of errors from temperature expansivity is being minimalized by measuring the temperature of the measure during the measurement and by following corrections from the difference between the current temperature and the nominal temperature of the measure. The nominal value of the temperature of the used measure is the temperature given by the producer, where the nominal dimension of the measure was given. Usually, it is requested, to perform the comparison and calibration of the measure at this temperature. Correction of the length from the temperature change of the measure is in technological practice given as a relation:

∆d = d ( t − t0 ) α

(1.2)

where d is the measured distance (m). t is the temperature of the measure during the measurement (°C). t0 is the temperature of the measure during calibration (°C). α is the extension coefficient of material of the measure (for steel is α = 11. 10−6 °C−1 up to 14.10−6 °C−1).

1.2  Environmental Conditions and Their Impact on Measurements

7

For most of the practical tasks, it is enough to know that at temperature change Δt = (t − t0) by 5 °C changes the length of 20 m steel tape by 1.2 mm. If it is necessary to assess the accuracy of the temperature difference Δt = (t − t0) , then by differentiating the Eq. (1.2) and by expression in the form of standard deviation (using Taylor’s law of propagation) will be applicable



σ ∆d =

σd α. d

(1.3)

At very accurate measuring, it is very complicated to assess the errors caused by temperature changes, because except the size of measured dimension, temperature expansion of the measure, and its temperature, these errors depend also from the temperature and temperature expansion of the measured object. The object temperature is usually measured by contact thermometers or thermometers based on thermovision technology. Vibration has a very special position among the impacts of the environment on measurement in industry. The vibration of the floor or ground appears in places, which are close to transportation ways. If a heavy truck passes by, when measuring, it is necessary to stop measurement for a while. The truck movement creates vibration in the leveling instrument and the image of the staff in the vision field wobbles. Therefore, it is impossible to target on the staff scale correctly, or to make the reading on the bar code staff. Vibration caused by moving sources (transportation vehicles, cranes) is temporal, and after their passing by, we can continue the measurement. A different situation is when the source of vibration is static, and it creates vibrations consequently. The vibration of this kind is typical for turbine generators, pumping devices, power supplies, ventilators, mills, compressors, and many other devices powered by electric or diesel engines. Leveling in such environment is very demanding and its accuracy depends on the intensity of vibration. When leveling with classic levels, the telescope bubble wobbles together with the level in such an environment. The wobbling is not only in transversal direction but in lengthwise, too. The outline is shaky and less visible. However, it is possible to settle the level and measure despite wobbling. When leveling with automated levels (levels with compensator), the situation is different. In consequence of resonance, the tripod and the compensator wobble, which is seen in the image of the staff, or its scale (Fig. 1.5). The wobbling of the image is at automated levels multiple times larger, than at measuring with classical levels. The impact of vibration can be limited by: • Looking for such a place on the floor of the building, where the vibration is the least perceivable • Positioning the level the lowest possible (we open the tripod legs the most possible) • Shortening the line of sight • Light holding the tripod head or the instrument during measurement

8

1  Specific Conditions of Geodetic Measurements in Industry

Fig. 1.5  Vibration impact on the bar of the staff scale (image of the level’s field of vision)

1.3  Safety Regulations of Industry Measurements Geodetic work in industry is usually done among different technological devices and machines during their full operation. Measurement is often hindered by moving tracking and other vehicles, cranes carrying cargo and moving technological units of production lines. To other hindering elements belong also specific operation limitations, which do not allow to measure according to standard custom practice and processes (time limitations, limitations in positioning the instrument, safety risk which limits moving of the measuring group, etc.). In such conditions, it is very important to respect the safety regulations, which are both of general character, but of specific character for a specific operation, too. The head of the measuring group is responsible for health protection and safety not only for himself/herself but for the whole group. Therefore she/he needs to respect general health and safety instructions and regulations of the particular operation space, and she/he needs to inform also other group workers. When entering the industry premises, it is necessary to meet with the safety technician of the plant, who informs every member of the group about regulations, to assure safety and health protection at work on the premises. Followingly, the technician prepares a protocol about safety training, which has to be signed by all members of the group. In each plant, it is required to attend safety training and to use safety and protective aids. It is very important to have adequate clothing, sturdy (nonslippery) footwear, reflective tapes or elements, and safety helmets. If the surrounding is dusty, it is recommended to use respirators. When working at night or in dark spaces, each worker needs to have a torch or safety helmet with built-in lighting. At some premises, the measuring group needs to carry a first aid box during the whole measuring process with them. In chemical operations and in an explosive environment, we need to respect specific safety regulations. When entering such premises, the measuring group has to be trained specifically for this type of operation space, and it is necessary to use protective aids and clothing with the antistatic finish. Sometimes, safety confirmation about used instruments and equipment can be required that they are appropriate for use in an explosive environment.

1.3  Safety Regulations of Industry Measurements

9

For work at the height, it is required to have a confirmation from a general practitioner and to attend specific training with a focus on such work. All workers working at height need to have specific safety harnesses and fall arrests, by which they fix themselves and protect themselves from falling. The head of the measuring group is responsible for the safety of all members, if she/he is not working at height, too. In the noisy environment, it is necessary to use hearing protectors (dampers), which leads usually to limitations in communication between the measuring personnel even in the immediate vicinity. When working with laser, it is required to work with special protective glasses and to respect specific regulations. Very possible risk of injury in premises of production, industry, and in plants can be caused by operation vehicles. Predominantly in older plants, which have smaller premises, the measurement is more complicated because of the transport, sometimes to such an extent, that it is nearly impossible to do the measurement. This has a crucial impact on the work of the measuring group, its processes and on decision-­ making, and which instrument to use. In such premises, there are not only vehicles of general transport like trucks, automobiles, or tractors but also accumulator trolleys towed trailers, tracked vehicles, mobile or rotary cranes, clam-shell buckets, etc. Safety and health protection against electric shock is very important, too. During setting-out and control measurement, the measuring personnel usually move around electrical equipment, machines, and devices. In such cases, it is necessary to keep every member of the group informed and to ensure their awareness with restrictions, regulations, protection zones of particular devices, and about risks of injury by electric shock. Based on the mentioned above and depending on the character and level of protection, it is common to require from the measuring group (which will do the geodetic work in the premises of the plant) to attend the training in advance. Usually, the trainings are: • • • •

On safety and health protection at work On work at height On radiation Psychological tests

After undergoing the trainings and tests, applicants get a confirmation/certificate, which entitles them to work in that specific environment. These certificates have only terminable validity, which depends on how successful the candidate was at testing. Some of the training focused on the specificities of a particular plant or operation is valid only in that very specific environment. Noncompliance with safety and health protection regulations and instructions, predominantly not wearing protective equipment, usually leads to agreement/contract cancelation. The contractor of geodetic works then risks also financial or other forms of sanctions, which can lead to the prohibition to work at the premises of a plant.

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1  Specific Conditions of Geodetic Measurements in Industry

1.4  Accuracy Requirements of Industry Measurement Accuracy in industry can be assessed from two viewpoints: Firstly, from the viewpoint of accuracy required at assembly and building of machines and equipment, mainly their moving parts, and secondly, from the viewpoint of the production and the montage of steel structures. Requirements on the accuracy of machine and equipment assembly are very high and hardly achievable with geodetic methods. With this part of accuracy deals a discipline called “fitting.” Each machine or equipment consists of components, whose geometry (shape) is given by their function and relation to other components. The shape of the component is given by its dimensions. Geometric dimensioning and tolerancing (GD&T) is a system for defining and communicating engineering tolerances. The component of specified dimensions cannot be produced with absolute accuracy. Its actual size (manufacturing dimension) will be always a little bit different from the right dimension (fundamental dimension). To define the deviation of the basic dimension (basic size) of the component from the manufacturing dimension and to limit it with regard to its function, the term “tolerance” has to be introduced. Tolerance is a numerical value describing an acceptable variation in component’s dimension (acceptable quality level), without significantly affecting functioning the final product (machines, structures, etc.). It is a difference between the upper and the lower accepted limits of the component’s dimension. If the component is good, its real manufacturing dimension is within tolerance. Limiting values of deviations are usually given by a numerical value of deviation (fundamental deviation) from the basic dimension. Tolerances can be applied to any dimension. When designing mechanical components, a system of standardized tolerances called International Tolerance Grades is often used (Table 1.1). Components can have machined or rough surfaces. Some of them are free, i.e., they are not in contact with other surfaces, whereas others are clustered – they are in contact with other component surfaces. Fitting (dimensional fit) is a general term for the accuracy of the machining and the relation between dependent components, which are joined or arranged together (Fig. 1.6). The method of standard tolerances is also known as Limits and Fits and can be found in ISO286-1:2010 Geometrical product specifications (GPS). ISO code system for tolerances on linear sizes – Part 1: Basis of tolerances, deviations, and fits. In ISO 8015:2011 Geometrical product specifications (GPS), fundamentals – concepts, principles, and rules – are specified the principle of the relationship between dimensional tolerances and geometrical tolerances. It shall be applied to linear Table 1.1  International Tolerance (IT) Grades and their general applications IT grade

Measuring tool 01 0 1 2

3

4

5 6 Fits

7

Material 8 9 10

11

12 13 14 15 16 Large manufacturing tolerances

1.4  Accuracy Requirements of Industry Measurement

11

Fig. 1.6  Tolerance of components in mechanical engineering

dimensions and their tolerances, angular dimensions and their tolerances, and geometrical tolerances that define the following four aspects for each feature of the part: size (dimension), form, orientation, and location. Standards ISO 2768-1:1989 and ISO 2768-2:1989 discuss the topic tolerances for linear and angular dimensions and features without individual tolerance indications. When individual tolerance indications are not given could be calculated using tolerance unit

I = 0.45

3

D + 0.001 D

(µm)

(1.4)

where I is the tolerance unit. D is the dimension in mm. The quality (accuracy) of production and assembly of steel structures is handled also in the standard EN 1090-2:2018 Execution of steel structures and aluminum structures – Part 2: Technical requirements for steel structures. The standard divides

12

1  Specific Conditions of Geodetic Measurements in Industry

steel structures into four execution classes: EXC1 to EXC4. Execution classes can either apply to the whole construction or to its parts or details of components. Construction can have several execution classes, too. If the execution class is not given, then the construction is considered to be in the execution class EXC2. The most important and frequent measurement in the industry is the measurement of lengths (dimensions, sizes). Measuring dimensions can be divided into four groups according to accuracy: 1. Measurement with accuracy ± 0.001 mm and more. To achieve this accuracy are used different mechanical, or more frequently optical, pneumatic, electric, or combined instruments. The most accurate optical instruments for measuring dimensions are interferometers. 2. Measurement with accuracy ± 0.01 mm. To achieve this accuracy, micrometric measuring instruments could be used, which can measure the whole dimension. Dial indicators (indicating gauge) measure with the same accuracy. Those belong to the group of comparative measuring instruments because they show only the difference of the measured value from the previously set value. 3. Measurement with accuracy  ± 0.1  mm is done with slide gauges – depth and height gauges. This type of accuracy is required at the measurement of the component’s dimensions with less accuracy. 4. Measurement with accuracy ± 0.5 mm is defined in the industry as rough measurements. This is done by rod or steel measures (steel tapes), which scaling has a resolution at least 0.5 mm. Geodetic measurements are applicable for tasks in groups No. 3 and 4, rarely also in group No. 2.

Chapter 2

Quality of Industrial Measurements

Due to the intensive research in the field of development of sensors, measuring instruments or measuring systems, the level of industrial measurement is well developed. The quality of measurement is generally connected with using modern, high-quality, and verified instruments and measurement systems in the process. Parallel to this, the application of optimal methods with correct result assessment is required. Nowadays, wide standardization in measuring for the industry is considered to be a matter of course; however, the journey toward standardization was very demanding and not always easy. The chapter brings a short overview of the development in the field of industrial measurement, metrology, quality assessment, as well as the process of standardization and institutionalization. Finally, the basic rules and requirements of testing and valuation of geodetic equipment, instruments, and systems are introduced, and the list of international standards relevant to the discussed topic is presented.

2.1  Definitions and Terminology The level of measurement, measuring instruments and methodology, is recently very developed, mainly because of intensive research in the field of the development of sensors and measuring systems. The field of industrial measurement is an integral part of this process, not excluding measurements done in an industrial environment. The quality of measurement is generally connected with using modern, high-­quality, and verified measurement instruments (measurement systems) in the process of measurement, with application of optimal methods and with high accuracy result assessment. Nowadays, wide standardization in measuring is considered to be a matter of course, as well as the use of a common system of units almost all over the world, and unified metric system use. However, the journey toward standardization was very demanding and not always easy.

© Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_2

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2  Quality of Industrial Measurements

Historical development in this field focused predominantly on the definition of terms and on the standardization of measures. The adoption of the document “Magna Carta Libertatum” in 1215 in England, which was adopted also the unit of length – yard, was the first and very important step of this way. Spreading the metric system to Europe was a significant milestone leading toward the current common system of units, as well as adopting it by France, the Netherlands, and Belgium in 1795. One meter had been stated as a basic unit of this system, at those times defined as 1/10,000,000 of the quarter of the Earth’s meridian quadrant. By the same document had been adopted also the unit of weight – 1 kg, as a weight of 1 l water at its highest density and at the temperature of 3.98 °C. By institutional anchoring of the standardization process, 18 states had signed a Meter Convention (Argentina, Belgium, Brasil, Denmark, France, Germany, Norway, Peru, Portugal, Austria-Hungary, Russia, Spain, Switzerland, Italy, Turkey, the United States, and Venezuela). Based on this document was established the International Bureau of Weights and Measures (Bureau International des Poids et Mesures – BIPM) with its seat in Paris. It means not only a distinctive move forward in measures standardization, but this institution is the first to represent measure activities on the international level. Measurement is a process, and its result is a value of the measured parameter. There are wider or more specific definitions of the term “measurement.” According to the way of defining the parameter, we distinguish direct and indirect methods of measurement. By indirect methods of measurement, we gain the measured quantity by measuring other quantities, which are in functional relation with the measured quantity. Methods of measurement describe physical principles of the measured value, as well as the measurement methods used for testing or evaluation. Metrology is defined as a set of activities and knowledge related to measurement. It includes theoretical and practical aspects in relation to measurement with no regard to their level of accuracy as well as the scientific or technological field. We usually distinguish scientific (theory of measurement), legal (describing legal directives, norms and other technical regulations of metrological character), and industrial (connected with regular measurements in practice) metrology. This categorization is conventional and is used for the detailed distinction of metrological fields. Metrology is defined by these subjects and activities of the measurement: • • • • •

Measuring units of physical and technological quantities Measures Methods of measurement Subjects of measurement Measuring and determination of basic physical constants

Subjects of measurement are metrology workers (staff) who handle the measures, evaluate the results, and continuously ensure or enhance their professional qualification.

2.1  Definitions and Terminology

15

Quantity is a feature of a phenomenon, body, or material, which can be qualitatively distinguished and quantitatively determined. The term quantity can be related to general or specific quantity. Quantities are, for example, length, time, weight, temperature, or electric resistance. Specific quantities are, for example, the length of a given bar, area of a given land, the temperature of the solution, etc. A basic measurement unit is a measurement unit of the basic quantity in the given system of quantities. In each coherent system of units is only one basic unit for each quantity. A system of seven measurement quantities (for quantities, length, weight, time, electric current, thermodynamic temperature, amount of substance, and candlepower) is the basic units of the International System of Units SI (Systéme International d’Unités). Derived units are associated with derived quantities and are not limited in number. To these belong the radian and steradian as the units for the plane and solid angle. Etalon is a materialized measure, instrument, reference material, or measuring system determined to define, realize, preserve, or reproduce the unit of one or more quantities. A complex of materialized measures or measurement instruments, which create an etalon, is known as “group (associated) etalon.” Etalons are further classified more in detail according to different attributes, e.g., international, national, primary, work etalon, etc. The relation is a feature of the measurement result or value of etalon, which is in relation to other determined/defined reference etalons – to national or international etalons, by a continuous sequence of comparison with determined uncertainties. The continuous sequence (chain) of comparison (calibration) is called the reference (sequence) chain. This concept (term) is often specified as “sequential or referring.” Reference and its sustainability is a very important attribute of correct measurement. The true value of the quantity is a value, which is in compliance with the definition of a specific quantity. It is a value, which can be obtained by correct measurement – measurement without errors. By its character, it is an undeterminable value. In practice, this value is replaceable by the convenience value or by the most probable value (established in mathematical statistics). This value can be achieved by measurement where systematic errors are minimized during the whole measuring process. To determine the convenience value, we usually apply the repetitive measurement principle. The measure is an equipment determined to define dimensions by itself or in connection to other equipment. It covers terms such as materialized measure or measurement instrument. A measure is, for example, a leveling rod, an EDM, a theodolite, or a measuring tape. However, a measure is not a leveling instrument without the leveling rod or fuel consumption gauge in a car. We usually distinguish measures and measurement instruments. Decisive factors of the accuracy of each measurement are measurement instruments’ scales. By means of the scales we determine the dimensions of other subjects. The higher the accuracy requirements of the measurement are, the more precise we need to know the values, which we read on the scales. Also, we need to verify these measures more precisely. It is very important to ensure the unification and accuracy of these measures, outgoing from

16

2  Quality of Industrial Measurements

construction principles and reference schemes of these measures. The same convenience (homogeneity) among all measurements can be achieved only by the mentioned above. Comparison, connection, and correct interpretation of the measured data can be applied only after ensuring the unity of the measures. Measuring range is a range in which the measure gives the result within declared uncertainties. When using measuring instruments and other equipment, we need to pay attention to the fact that the resolution of instruments is not the same as their real accuracy. It is necessary to take into consideration that actual dimension (value) of a real measure and of measurement instrument changes in time and within conditions and the accuracy given by producers is almost always higher than the real (achieved) accuracy. The correctness of a measure is the ability of a measure to give values close to the true value. Each correct measure shows results, which are within declared uncertainties. Error in the value indicated by the measure is the difference between the value of the measure and actual (convenience value) of the measured quantity. By the materialized measure, this is the value marked on the measure (nominal value). Error in the value indicated by the measure is one of the most important characteristics of the measure. According to this characteristic is evaluated the measure during its testing or verification. Errors in values indicated by the measure are determined by calibration. Verification is a procedure which verifies the accuracy of the measure. Verification using a comparison is a procedure which verifies the accuracy of the measure by comparison to measure, which has the accuracy of one level higher. The constant increase in the level of mechanization and automatization of measures and measurement processes leads to productivity increase, but also to increase in quality of production. In the area of measurement, this development brings step by step increase also in accuracy and quality of measurement results. Because of ensuring unity, correctness, and reproducibility of measurements and its results, it is necessary to pay attention to constant verification and calibration of the measurement instruments and devices. Calibration is a set of actions, which at defined conditions determine relations between values indicated by measure or measurement system or values represented by materialized measure or reference material and equivalent values realized by etalons. Calibration is a fundamental metrological activity; it is a specific measurement type with use of etalons. The result allows either to mark the values on the measure or to determine corrections to indications of the measure. Calibration can determine also other metrological features, for example, the effect of impacting values. The result of calibration is usually registered in the calibration certificate (assessment of calibration). Without using calibrated measures, we cannot ensure the quality of production or credibility of measurement results. From a methodology point of view, it is important to have different processes (methods) at disposal for different measurement instrument types. The measurement result is a value determined by the measure and achieved by measurement. Full information about measurement result includes also the

2.1  Definitions and Terminology

17

information about the measurement uncertainty. The result has to include information in form of a multiple number and unit of measurement and also information about uncertainties. Without this information, the measurement result is not complete. The measurement error is the difference between the measured value and the actual (convenience) value. According to the way of appearance, we distinguish systematic (Fig. 2.1), stochastic errors (Fig. 2.2), and blunders. Measurement uncertainty (uncertainty of measurement result) is a parameter allocated to measurement results. It characterizes the dispersion of values, which can be allocated reasonably to the measured value. This parameter can be, for example, sampling standard deviation or width of the reliability interval. Measurement uncertainty can generally include uncertainties of type A1 and type B2. In surveying

Fig. 2.1  Appearance of systematic errors 1  In type A evaluations of measurement uncertainty, the assumption is often made that the distribution best describing an input quantity given repeated measured values of it (obtained independently) is a Gaussian distribution. The input quantity then has expectation equal to the average measured value and standard deviation equal to the standard deviation of the average. When the uncertainty is evaluated from a small number of measured values (regarded as instances of a quantity characterized by a Gaussian distribution), the corresponding distribution can be taken as a t-distribution. Other considerations apply when the measured values are not obtained independently. 2  For a type B evaluation of uncertainty, often the only available information is that the input quantity lies in a specified interval. In such a case, knowledge of the quantity can be characterized by a rectangular probability distribution with limits. If different information were available, a probability distribution consistent with that information would be used.

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2  Quality of Industrial Measurements

Fig. 2.2  Appearance of stochastic errors

practice, usually, the “standard deviation” is used to determine measurement uncertainty. Correction is an algebraically added value to the un-rectified measurement result, which compensates for systematic error. Correction is the basic information resulting from the measurement calibration process. It equals the systematic error value adjusted, with the opposite sign. Systematic errors of the measure could be eliminated thanks to corrections, and by this correct results could be achieved. The correction curve is the graphic representation of corrections.

2.2  Quality Evaluation of Industrial Measurements The quality of measurement is a crucial parameter of measurement done in the industry environment. Opposed to the quality assessment used in surveying, based on mathematical-statistical evaluation of the accuracy (quality) of measurements, in the industry the quality is evaluated based on the reliability. According to

2.2  Quality Evaluation of Industrial Measurements

19

measurement realization and determination of their quality (accuracy), quality classes are defined: • Class C – the lowest quality, when the result is only one value without any other information and additional values characterizing quality, this type of measurement is usually considered to be informative only. • Class B – the measurement result contains also value about quality (accuracy) of the measurement in a form of marginal values of the interval, in which the real measured value is positioned. To determine the interval, we usually use information from producers, which means that the level of reliability of values limiting the interval is given by the level of “trust” in the information given by the producers. • Class A – measurement result contains also some value about the most probable measured value and about the interval, in which the real value is realized, given by characteristics representing statistical quality (accuracy) of the measurement. There is one specific class of quality, class AA, in which except for procedures and conditions of class A, we require also information about the real (actual) state of the measure based on information from documents (calibration sheets, certificates, etc.). Measurement should be done by a qualified person with experience in the area of measurement and metrology. We assume that when considering classes C and B, it is sufficient to do only one measurement (it is necessary to control the functionality of the measure and its parts and respect the producer’s recommendations for the measurement process). Measurements done in class A require, except for respecting the process and the method, also repeated measurements and use of mathematical-statistical methods. A part of the measurement is quality characteristics (accuracy) of the measurement, determined by statistical processing of repeated series of measurements. Exerted way of measurement evaluation in the industry is expressing the uncertainty of its result. According to international technical regulations, the uncertainty is defined as a non-negative parameter characterizing the dispersion of values, or an interval, where lies the correct value, too (VIM3, ISO 3534), similarly to the interval, into which can be rightfully realized to the measured value. The basic qualitative characteristic of the uncertainty is a standard (complete) uncertainty

u = uA2 + uB2 ,



(2.1)

which contains uncertainty of: • Type A – is determined by application of mathematical-statistical processes, by an increase in the number of repeated measurements done at the same conditions their value decreases. • Type B  – is determined by the identification and quantification of the known sources of errors. Usually, the low of error propagation is being applied.

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2  Quality of Industrial Measurements

The type A uncertainty is usually determined by



sx

uA= s= x

, n

(2.2)

where: sx is the sampling standard deviation of the measurement series. sx is the sampling standard deviation of the particular measurement. n is the number of measurements done at the same conditions. By determination of the uncertainty of type B, it’s necessary to identify all possible error sources, which were not included in the uncertainty of type A. It could be included here information and specifications given by the producer of the measure, information from certification sheets, information achieved from previous measurements, and general knowledge and experience about materials and their features, about used measurement instruments and measures. There is often used also a simplified method of calculation of the uncertainty of type B by using the maximum (possible) error given by the produces Δxmax in a form



uB =

∆xmax 3

(2.3)

,

in the case of a normal probability distribution. The “Guide to the Expression of Uncertainty in Measurement,” commonly known as the GUM, is the definitive document on this subject. The GUM has been adopted by all major national metrology institutes, by international laboratory accreditation standards such as ISO/IEC 17025, and employed in most modern national and international documentary standards on measurement methods and technology (JCGM 200 2012).

2.3  Metrology of Industry Measurement The need for a worldwide unified system of measures became very important. The initiative of scientists of several countries resulted in a diplomatic conference held during the first universal industrial exhibition in Paris in 1875. During this conference, 17 governmental representatives signed a diplomatic treaty, which was known at that time as the Meter Convention. A decisive step for institutionalized anchoring of the standardization process and implementation of basic measurement units in the international system was the decision of signatories of the Meter Convention to establish a consistent state institution, the International Bureau of Weights and Measures (Bureau International des

2.3  Metrology of Industry Measurement

21

Poids et Mesures – BIPM), with its seat in Paris. This bureau was first to represent metrology activities on the international level. The highest authority in the area of international metrology, which accepts decisions of fundamental principle, is the General Conference (general assembly) of the member states of BIPM. The first general assembly was held in 1889 and is organized every 4 years. Activities of the bureau between general conference meetings are directed by the International Committee for Weights and Measures (Comité International des Poids et Mesures – CIPM). The basic mission of BIPM is coordination of activities leading to the creation and maintenance of the unified international measurement system, with an aim to provide accurate and comparable results of measurements (BIPM 2019). BIPM fulfills its mission through the development of the technical and organizational infrastructure for the International System of Units (SI), which is the inevitable basis for demonstrability and comparability of measurement results worldwide. With this aim, it monitors collaboration and cooperation among laboratories of particular national metrology institutions (NMI). To ensure high level and quality of provided information, as well as of support of metrological activities done at the international level, CIPM established Consultative Committees for areas: • • • • • • • • • •

Acoustics, ultrasound, vibration (AUV) Electricity and magnetism (EM) Length (L) Mass and related quantities (M) Photometry and radiometry (PR) Amount of substance (QM) Ionizing radiation (RI) Thermometry (T) Time and frequency (TF) Units (U)

CIPM also ensures the coordination among international comparison measurements by using nationals reference etalons, defining and maintenance of suitable reference etalons for the realization of international comparative measurements at the highest level. It fulfills the aim of a coordinative laboratory for chosen comparative measurements, for the realization of specific calibration activities for the member states and for joining and coordination of activities of national and international organizations and institutions. CIPM further provides information about publications, organized seminars, and conferences for the needs of the scientific community, experts, and professionals in the area of metrology. One of the last activities to be soon fulfilled is also publishing of the international metrology dictionary. The last up-to-­ date version is available under the code VIM3 (JCGM 200 2012). For the area of legal metrology, in 1955 had been established the International Organization of Legal Metrology (OIML). The purpose of OIML is to promote global harmonization of legal metrology procedures. The OIML supports national

22

2  Quality of Industrial Measurements

metrological institutes in their activities with metrological guidelines for the manufacture and use of measuring instruments for metrology applications. Currently, the OIML is composed of 61 members and 61 corresponding members (OIML 2019), and their activities are managed by the International Committee of Legal Metrology (CIML). The CIML is the functional decision-making body of the OIML.  CIML members (one per member state) are designated by their government. They are in principle officials in the department concerned with measuring instruments or have active official functions in the field of legal metrology. Participating in OIML work allows members to receive up-to-date information from other participants concerning new technologies, ways to assess the conformity of instruments, solutions found in other countries to answer specific problems, good practices in legal metrology, experience in the organization of legal metrology activities in different countries, etc. Members may influence the OIML’s policy and provide input to the OIML Strategy so that their needs are taken into account in the Organization’s work. The Strategy deals with the general policy of the Organization, as well as with the support the OIML offers to national legal metrology authorities and to all its members, and specifically those in developing countries. OIML members can benefit from participation in the OIML Certification System, which allows OIML Certificates and/or OIML type evaluation reports issued by OIML Issuing Authorities in the OIML member states to be accepted by other participants as the basis for issuing national or regional type approvals for several commonly regulated categories of measuring instrument. In the continual globalizing world, it is very important for both the producers and the users, to know that the product meets the given or by the producer declared specifications – conformity assessment. A basis for this kind of assessment is measurements, for which the methods of calibration are known, testing, as well as the process of their certification. There is a set of international standards, covering these activities and defining the procedures for all steps (Table 2.1), produced by the special committee of ISO –ISO CASCO Conformity Assessment. The assurance of competence of the bodies participating in the conformity assessment is declared through their accreditation. The world’s principal body for laboratory accreditation is the International Laboratory Accreditation Cooperation (ILAC), which provides an evaluation of conformity assessment bodies against recognized standards to carry out specific activities to ensure their impartiality and competence. ILAC is the international organization for accreditation bodies operating in accordance with ISO/IEC 17011 and involved in the accreditation of conformity assessment bodies including calibration laboratories (using ISO/IEC 17025), testing laboratories (using ISO/IEC 17025), inspection bodies (using ISO/IEC 17020), and proficiency testing providers using ISO/IEC 17043 (ILAC 2019).

2.3  Metrology of Industry Measurement

23

Table 2.1  ISO standards relevant to conformity assessment Scope Supplier’s declaration Calibration and testing

Inspection/ accreditation

Certification

General

Relevant ISO standards ISO/IEC 17050:2004 Conformity assessment – Supplier’s declaration of conformity ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories ISO/IEC 17034:2016 General requirements for the competence of reference material producers ISO/IEC 17043:2010 Conformity assessment – General requirements for proficiency testing ISO/IEC 17011:2017 Conformity assessment – Requirements for accreditation bodies accrediting conformity assessment bodies ISO/IEC 17020:2012 Conformity assessment – Requirements for the operation of various types of bodies performing inspection ISO/IEC 17040: 2005 Conformity assessment – General requirements for peer assessment of conformity assessment bodies and accreditation bodies ISO/IEC GUIDE 23:1982 Methods of indicating conformity with standards for third-party certification systems ISO/IEC GUIDE 27:1983 Guidelines for corrective action to be taken by a certification body in the event of misuse of its mark of conformity ISO/IEC 17021: 2015 Conformity assessment – Requirements for bodies providing audit and certification of management systems ISO/IEC 17023: 2013 Conformity assessment – Guidelines for determining the duration of management system certification audits ISO/IEC 17024: 2012 Conformity assessment – General requirements for bodies operating certification of persons ISO/IEC 17026: 2015 Conformity assessment – Example of a certification scheme for tangible products ISO/IEC 17027: 2014 Conformity assessment – Vocabulary related to competence of persons used for certification of persons ISO/IEC 17028: 2017 Conformity assessment – Guidelines and examples of a certification scheme for services ISO/IEC 17065:2012 Conformity assessment – Requirements for bodies certifying products, processes and services ISO/IEC 17067:2013 Conformity assessment – Fundamentals of product certification and guidelines for product certification schemes ISO/IEC GUIDE 60:2004 Conformity assessment – Code of good practice ISO/IEC GUIDE 68:2002 Arrangement for the recognition and acceptance of conformity assessment results ISO/IEC 17000:2004 Conformity assessment – Vocabulary and general principles ISO/IEC 17007:2009 Conformity assessment – Guidance for drafting normative documents suitable for use for conformity assessment ISO/IEC 17030: 2003 Conformity assessment – General requirements for the third-party marks of conformity ISO/IEC 17033: 2019 Conformity assessment – Ethical claims and supporting information – Principles and requirements

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2.4  G  eodetic Equipment and Instrument Testing and Evaluation Opposed to other measurement systems and instruments, geodetic instruments are different in their use, precision, and quality of production (responsibility). Geodetic instruments are, however, not used in constant (changeless) laboratory conditions, and by their frequent transport, they are often exposed to collisions, concussions, and vibrations. They are also exposed to changing physical conditions, which again causes a change in their parameters, features, and characteristics. Verification of parameters of geodetic instruments is therefore very important not only because of documentation of their current state but has a direct impact on the quality of results of measurements done by this equipment. By process validation we detect the real characteristics of verified instruments and determine their real accuracy, and by all this, we also can state the accuracy of the measurement. Geodetic equipment undergoes the first validation process already during its production. This validation has a character of a series of testing, and it should evaluate whether technical parameters of instruments did not exceed the production deviation. By this kind of testing, we prioritize the economy point of view, and therefore such information should be for the user’s more informative character. Therefore, it is very important to validate all the parameters of the instruments also continuously during their use in the field. Results of such validation tests are very important because of quality, stability, and other features of used equipment and at the determination of corrections of measured values. They are very precious and very useful for the development of new measurement processes and methods, for preparations and realizations of measurements in very specific conditions, as well as at researches. The result of the validation of instruments is the determination of values of their parameters, which characterize the current state of the instrument. The deviation of these parameters from information given by the producer means the need for rectification of the instrument or implementation of corrections to the measured values. Current values of the instrument’s parameters, including the evaluation of its state, became a part of the protocol about the testing or the calibration certificate (Fig. 2.3). In case of need to implement corrections to the values of the instrument, the result is a functional relation enabling calculation of corrections for the specific measured value, or a table of corrections listing the corrections with sufficient detailed information depending on the resolution function (Fig. 2.4). A series of the international ISO system, which is in competition of ISO TC172 SC6 Geodetic and surveying instruments (Table 2.2), brought a high level of standardization in the field of geodetic instruments’ verification. Norms contain processes for measuring in laboratories or in the field, methods of processing, and result evaluation including their interpretation. Processes anchored in norms for testing of geodetic instruments in field are adjusted for the field conditions, they use equipment and instruments given by producers, and they do not require specific or complicated equipment, which is connected to testing in laboratories.

2.4  Geodetic Equipment and Instrument Testing and Evaluation

Fig. 2.3  Calibration certificate of a leveling system calibration

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Fig. 2.4  Table of corrections of leveling staff

2  Quality of Industrial Measurements

References

27

Table 2.2  ISO standards relevant to geodetic instruments testing Scope Laboratory testing

Relevant ISO standards ISO 9849:2017 Optics and optical instruments. Geodetic instruments. Vocabulary ISO 12585-1:2014 Optics and optical instruments. Ancillary devices for geodetic instruments – Part 1: Invar leveling staffs ISO 12585-2:1999 Optics and optical instruments. Ancillary devices for geodetic instruments – Part 2: Tripods ISO 12585-3:2005 Optics and optical instruments. Ancillary devices for geodetic instruments – Part 3: Tribrachs ISO 16331-1:2017 Optics and optical instruments. Laboratory procedures for testing surveying and construction instruments – Part 1: Performance of handheld laser distance meters Field procedures ISO 17123-1:2017 Optics and optical instruments – Field procedures for for testing testing geodetic and surveying instruments – Part 1: Theory ISO 17123-2:2001 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 2: Levels ISO 17123-3:2001 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 3: Theodolites ISO 17123-4:2012 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 4: Electro-optical distance meters (EDM) ISO 17123-5:2018 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 5: Total stations ISO 17123-6:2012 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 6: Rotating lasers ISO 17123-7:2005 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 7: Optical plumbing instruments ISO 17123-8:2015 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 8: GNSS field measurement systems in real-time kinematic (RTK) ISO 17123-9:2018 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Part 9: Terrestrial laser scanners

References BIPM (International Bureau of Weights and Measures). (2019). Work Programme 2016–2019. https://www.bipm.org/utils/en/pdf/BIPM-Work-Programme_2016-2019_final.pdf. Accessed 9 Dec 2019. ILAC (International Laboratory Accreditation Cooperation). (2019). https://ilac.org/about-ilac/. Accessed 12 Dec 2019. JCGM 200. (2012). International vocabulary of metrology – Basic and general concepts and associated terms (VIM) (3rd ed.). Sevres: BIPM. http://www.bipm.org/en/publications/guides/vim. html. Accessed 15 Jul 2018. OIML (International Organization of Legal Metrology). (2019). http://www.oiml.org/. Accessed 12 Dec 2019.

Chapter 3

Maps and Information Systems of Industrial Plants

Maps used in the investment process, which are completed by specific content custom to the industrial plant and equipment, are important information sources. Surveying documents create a major part of documents used for design as well as the operation of industrial objects (plants). This chapter presents the factory base map and its design, creation, and update during the plant’s life cycle. The main accent is given to the data collection according to the specific content of the factory base map as well as the specific conditions which are in plants. In the second part of the chapter, the basic principles, requirements, and methods of creating the industrial plant information system are presented.

3.1  Large-Scale Base Maps Surveying documents create a major part of documents used for design as well as the operation of industrial objects (plants). Maps used in the investment process, which are completed by specific content custom to the industrial plant and equipment, are important information sources. During the creation of these documents, we usually use national large-scale maps, which represent the whole territory of a state with basic general useful content. They are created within unified rules. These maps are published by governmental authorities, which use actual data of the state information system of geodesy, cartography, and cadastre during the creation of a map. To support the investment process, these maps are usually used of scale 1:5000 and larger. In many countries, these are known as large-scale base maps. According to the scale of a final map, in the past were introduced accuracy classes, which described the relationship between the accuracy of mapping and the scale of a map (Table 3.1). Modern surveying technology (including photogrammetry and mobile mapping), used for data acquisition and mapping nowadays, is able to ensure accuracy

© Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_3

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Table 3.1  Proposed map scales for different accuracy classes Accuracy class 1 2 3 4 5

Mapping accuracy [m] Measuring point position 0.04 0.08 0.14 0.26 0.50

Measuring point height 0.03 0.07 0.12 0.18 0.35

Map scale 1:200 (500) 1:500 (1000) 1:1000 (500; 2000) 1:2000 (1000; 5000) 1:5000 (2000)

required for classes 1 and 2, also in cases, when maps of scale 1:1000 or smaller are being produced. Thematic maps are created from information based on the general content of the state information system of geodesy, cartography, and cadastre, completed by specific information (content). Thematic state maps represent the whole territory of a state, including objects and content of natural, social, economic, and technical features and relations. These are created according to unified rules, usually defined for state base maps, and are published by a governmental institution. Thematic state maps are divided into groups according to their intent and are known as maps for: • • • • • • • • • • •

Design and urbanism Land planning and development Administration Land management Forest and water management Documentation of historical objects and buildings Operation of lines Design and operation of transportation structures Design and operation of underground structures Geological and hydrogeological research And others

To large-scale thematic maps belong, for example, the city base map, airport base map, highway base map, railway base map, factory base map, mine base map, etc.

3.2  Factory Base Map Design and Creation The factory base map is a large-scale thematic map created according to rules and standards relevant to (1) thematic large-scale maps and (2) specific content, requirements, and conditions of industrial plants. They represent in detail objects and technical equipment of the industrial plants, as well as their area of interest (surrounding), which are on, over, and under the ground. The factory base map is created with an aim to support activities connected to the planning, design, and operation of the

3.2  Factory Base Map Design and Creation

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factory. They are of fundamental importance because they help in evidence and inventory of buildings, lines, and technical factory equipment. The factory base map creates a base for many other documents used during the plant operation – factory railway map, station bills, maps for handling accidents, etc. It is the necessary document for mapping, for cadastral measurements, and for preparation of cadastral plans in the factory. This map is created on the base of data of large-scale base maps or other large-scale maps with general content and is completed by objects and details by measurement in the terrain. In case when a large-­ scale base map with general content is not at disposal, the factory base map is created from data collected by direct measurement in the terrain of accuracy class 2 or 3. The factory base map is created in national reference systems, except plants with their own reference system defined in the past. In most of the countries, the exception is given only with the approval of the national authority. The basic scale of the factory base map is 1:500. According to the density of measured objects (details), we can use scales of 1:1000, 1:250, or 1:200. Before the scale of the map is determined, a detail of the map’s content mainly from the point of view of the good lucidity should be analyzed. The size and layout of map sheets are in coherence with the layout of the national large-scale base map. The shift in the layout is possible in case when the whole area of a factory may be presented in one map sheet. The map sheet could be shifted by 100 m in the direction of both the X and Y axes. The size of the map could not be changed when the map is shifted. The data outside the map frame include the factory name, map title, reference frames, name of the author, date of data collection, and the scale (Fig. 3.1). The content of a factory base map consists of planimetry, hypsography, reference frame, reference points, and the map lettering. The content of a map includes all objects usually represented on the base large-scale maps as well as the objects important for the plan operation (roads, rails, cranes, chimneys, lines, pipes, etc.). The base of the correct data collection and map creation is the reference frame, in which configuration and density are appropriate for the realization of measurements (mapping). Resolution of the measured distances and data processing (coordinates) is higher as usually in the case of mapping and is defined at the millimeter level (three digits). Reference points are stabilized in places with compact coverage (concrete, asphalt) or in the upper structure of roads and footways. It is appropriate to protect these by a steel cover (Fig. 3.2). The planimetric content of a map includes borders (cadastral, owners, users, buffer zones, protecting areas), objects, and structures important for the plant operation (with temporary and non-temporary characters). To these belong buildings, production and storage halls, garages, transportation structures, technology equipment, lines, etc. Buildings and halls are marked on the map with their entrance, number of floors, as well as the height of their ground floor. The content of a factory map planimetry is completed by objects and equipment with specific assignment, for example, rotary kilns, blast furnaces, gas storages, water tanks, cooling towers, etc. The outlines of buildings and halls are highlighted by gray color, or the whole objects are gray-colored.

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Fig. 3.1  Factory base map – data above the map frame Fig. 3.2  Point stabilization in the upper part of the road structure

The group of transportation structures is represented on the map with their ax lines  – railways including factory railways, cableways, conveyor lines, bridges, footbridges, all kinds of gateways, crossings, tunnels, etc. All footways, edge stones, traffic islands, all kinds of lamps, semaphores, and lighting columns are marked in the map. Measurement of railways includes the definition of switchblades, labels, protecting cases, as well as other equipment necessary for the fluent operation of the traffic. Special attention is given to underground objects and lines. Their position is registered from documents of their operators and protocols given by them. The operator of these lines should provide information about size, material, as well as medium, which is transported by the given line. The search of lines using different locators should be used only in case when information about the line is missing. The uncertainty of this information is marked in the map with dashed lines. In case of a very high density of lines on a given place or when lines are installed inside collectors, the only position of one line is marked in the map, and information about other lines in the collector will be given in the form of text blocks. Also, the position of nonoperating lines is measured; the information about that is marked in the map.

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The hypsometric content is represented by elevation quotes, contour lines, or hachures. The base for measurement of heights and creation of the map hypsometry is the reference frame, which points are stabilized by benchmarks, usually in base of buildings and halls. The distance between two neighboring points should be no longer than 200  m. The reference frame is connected to the national frame of heights. Heights of points, which are on the surface with compact coverage, near the entrance of buildings and halls and the heights of different hinged doors are defined by using quotes. These heights are determined with an accuracy of 0.01 m (Fig. 3.3). The process of the factory base map creation follows the project (plan) of the base map production, which formulates general rules of methodology of data

Fig. 3.3  Example of a factory base map in analog form

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collection and processing, rules of use of existing data and documentation, as well as the borders of the locality (in case when only the factory map of a part of the plant is being produced), the reference frame and the numbering of additional points (densification of the frame), and other actions (entrance allowance for the team, safety measures, training, etc.). Author of a new map should collect all existing documents and maps as well as results of geodetic measurements made in the past related to the factory base map creation (in situ drawings, calculations, measuring originals, printing originals, etc.), as well as information about points, which build the factory reference frame. An important part of this documentation is the overview of all measurements related to the factory base map creation made in the past. The preparation of the digital factory base map and its form (structure) are not regulated today. The content of the map is usually arranged into layers and files using the software, which enables the creation of lines, markers, and objects according to existing general rules for the production of digital maps. The aim of recognition is to state more precisely the workflow of the map production. First of all, we evaluate facts, which are significant for the workflow management, and then the decision according to the used measuring methods, identification of underground lines and objects including evaluation of reliability of this information, as well as the work safety. Next, we evaluate the usability of collected archive documents and their correspondence with the current state (situation). Predominantly we evaluate the characteristics of a locality (density, size, and complexity of objects), terrain characteristics (morphology, accessibility), traffic inside the factory (intensity, volume), and, according to these, the planned consumption of time and financial resources. According to the signed agreement, we exactly identify borders of the area (locality) of interest. Any ambiguities (dimness) are cleared in collaboration with the ordering part (factory representatives). After recognition of the area of interest and according to the required accuracy, the prepared project and efficiency of realized works are specified: • Extent of densification of the reference frame • Given mapping method or combination of mapping methods if it is efficient The polar method is most frequently used to measure objects of the planimetric component of the factory base map. In the past, the method of rectangular coordinates and the method of control measures were dominating. In some cases, we applied the method of forwarding intersection and chosen methods of photogrammetry. The most efficient method of data collection nowadays is terrestrial laser scanning, which could be combined with other methods. The accuracy of measured points is given by the accuracy characteristics reliable for the second class. To measure the hypsometric components of a map, we use methods of leveling – known as technical and area leveling. The polar method could be used to determine measuring points on non-compact surfaces (free terrain). Heights of points on compact surfaces and heights of chosen objects are determined with the first-class accuracy and the points on non-compact surfaces with the third-class accuracy.

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The measuring content of a factory base map includes buildings and equipment, transportation objects, pipes and electricity, water lines and tanks, underground objects, vegetation and non-compact surfaces. Buildings are determined by their section with the terrain. Their measurement includes building entrances, passages, stairs, all details over 0.1 m to the level of the second floor. Entrances are identified by their size, brightness, and height. Using direct measurement we determine the height of the first floor, doorstep by the entrance, and relative heights of ramps according to the road. In the case of portal structures, we should measure the concrete base of pillars (their section with the terrain), pillar axes, and the supporting structure. When the building (hall) is built on pillars, the part over the ground will be measured. Equipment and pipes, which are between the building and the ground, belong to the technology installed inside the building, and therefore they are not measured during the measurement of a building (civil engineering structure). Supporting walls, fence, fuel stations, bridges between buildings, bridge balances, communication points, lift shafts, chimneys, and ramps and stairs outside the buildings and halls are all measured. If chimneys are not accessible, their center point and radius are determined by using non-direct measurement. The height of the chimney is determined, too. In the case of measurement of sewerage stations, cooling towers, and water tanks, their position and the height of the in-/outflow points are measured. Measurement of technology equipment (rotary kilns, gas storages, chemical rectors, blast furnaces, etc.) includes determination of their base, main axes, radius (diameters), connecting pipes, and other characteristic components. According to the complexity of these objects and the required detail, the appropriate generalization during the measurement is done. Roads and traffic lines are measured including all details and objects as footways, roadsides, channels, divider strips, road islands, bridges, tunnels, railway crossings, subways, supporting walls, lamps, semaphores, trolley line columns, etc. In the case of railways, all components and equipment, which support the fluent and safe operation of the railway, are measured – switches, gradient boards, traffic signs, stationing marks, ramps, service rails, supporting walls, bridge structures, railway balances, turntables, railway gates, etc. The switches are determined by the point of the beginning, the switch, and both endpoints. In the case of cross-switches, the middle point should be measured, too. The height of a railway is given by the height of the rail top. It should be measured in given distances and at points of rail crossing or when the rail enters the hall. When the railway has curved, the height of the inner rail top and the relative height difference between the rails should be determined. Cranes and crane runways installed outside halls are determined by their supporting structures (columns, pillars) and beams. The maximal length of the crane cantilever (boom) and its maximum load, as well as the height of the crane rail top, is determined. Conveyor lines are determined by their ax and brightness. The direction of the movement (operation) should be marked, and the positioning of a conveyor line should be determined (ground, overhead, or underground), too. The position of

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conveyor components (rollers, motors, drives, etc.) should be determined by their axes. At buildings and halls, the conveyor entrance points, as well as their height differences, height of overlaying parts, and the height of underpasses, are determined. The position and geometry of underground objects are determined by direct measurement of all visible parts. Non-accessible and non-visible parts of these objects are registered in the map using information from existing drawings (design). This should be marked in the documentation (technical report) of the map. The position of energy lines and operation pipes are marked on the map with their axes. The map content includes connection boxes, switch stations, transformers, converter stations, etc. The type of the line is determined according to given standards. Overground lines are determined by columns, wall-mounted consoles, lights, energy metering boxes, etc. If the column basement is visible on the terrain and its size and the map scale enable it to represent these in the map by drawing (not by badge), it is measured, and a drawing of the section (plan view) is drawn in the map. The position of all lines should be determined by measuring of sufficient amount of characteristic points. In the case of underground lines, we include in the map all lines, of which existence was detected by the map provider. All equipment or visible components (shaft coverage, entrance points, hydrants, etc.) of the underground line should be registered by measurement of their center points. In the case of pipes are determined their axes and diameter. Sewage lines could be different types, according to the material and the form of the line. Due to this, the cross-­ section of all sewage lines is registered. Collectors are measured inside, their size and position of all diversions are determined. If it is not possible to draw these on the map, only their axes are registered. All collectors should be measured and their cross-sections registered in each characteristic point of a collector. The position of all lines inside the collector is determined in the cross-section. If more lines are being installed in the collector, the position of all of them is necessary to measure. If a scale of a map does not enable visualization of all lines installed inside the collector, the axes of the installed lines should be drawn near the walls of the collector. If a map scale does not enable either the visualization of these lines, their common ax is drawn. If the lines are installed above each other, the position and a type of each line in the collector should be determined. This information is visualized on the cross-section of the collector. The methodology of measurement and determination of lines in the factory is usually regulated in given directives or standards. If they are in the area of interest of concealed lines, this should be adduced by the ordering part. The heights of canalization, collectors, pipes, or cable channels are determined usually in entrance shafts or cable chambers. The height of their underdrain and heights of all in-/outflows are determined in the shaft of canalization. Water flows are determined by the coastline, contour line of the water storage, the locks, water channels, lashers, water gates, streambeds, limnigraphs, wells, etc. The height of the streambed and water level should be determined by measurement. The date of measurement should be registered.

3.3  Factory Base Map Updating

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In the case of green mapping, we measure trees with a trunk diameter larger than 0.15 m. In that case, we measure also the diameter of the tree crown. The type of vegetation is usually determined according to specific standards. Results of the in situ detection and measurement are registered, and a field survey sketch is prepared in the terrain. According to the used measuring method, the form of the registration and the content of the survey sketches are given. The type and number of sketches prepared during the mapping are defined by the project of the factory base map. All sketches are titled by the name of the factory, the intent, and the number of the sketch. The preparation of field sketches is usually formalized by national standards or internal regulations. The final documentation of the factory base map includes the technical report, which describes the methodology and technique of data collection, as well as the valuation of data collected by former measurements and used for map creation. The chart flow of all measurements is described in the accompanying document (a record) prepared according to specific rules. The final documentation is completed by the project of the base map, a record about control made during the data collection and processing, other documents related to the map creation, calculations, coordinates and heights of measured points, sketches, etc.

3.3  Factory Base Map Updating Reconstructions and maintenance occur in industrial plants very often. Due to this, the up-to-date content of the factory base map is limited, when this is not regularly updated. Update of the factory base map includes all parts of the map content, mainly planimetry, hypsometry, and production lines. The base of the map update is information about the plant operation and investment projects, as well as information of providers of civil engineering works. Usually, the changes are registered by regular inspection walks done through the plant, mainly walks around parts, where construction works and reconstruction of buildings and halls or equipment are realized. Changes are measured with the same methodology and accuracy as during the original measurement (mapping). These changes are marked in copies of original field sketches; in case of large amount and density of changes, new sketches may be created. According to registered and measured changes, a new drawing is created and included in the actual part (component) of the base map. All changes in the base map content and documentation should be realized in written form with a time stamp. In the case of digital base map, new files are created, which include the new, changed content of the map. All files should include a label of their version.

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3.4  Information Systems of Industrial Plants The aim of information systems of industrial plants is the evidence of all objects and the estate property of the plant. The appropriate information system (IS) is able to support the management and daily operation of a plant, as well as provide up-to-­ date information, which supports decision-making in the field of investment, construction, and maintenance. IS defines tools, subjects, and structure of the property estate evidence and effective maintenance, as well as software, which is appropriate for processing and management of IS data. ISs of industrial plants consist of two parts – database and graphical part (maps). The database includes information about the plant property in the form of text documents, tables, values, pictures, drawings (sketches), etc. The graphical part consists of maps of different content, scale, and intent. The base of this part is the factory base map. Both parts of the IS are joined in interactive ways that enable visualization of data about selected objects in the map and opposite the view of objects is highlighted in the map when the object is selected in the database. Modern ISs operate only digital documents and maps in digital form. In the past, the evidence of the industrial plant property was operated in analog form. To make possible to include this information for the actual IS, the methodology and technology of transformation of old analog documents and maps to digital form should be defined. Quality of the old information is significantly influenced by any changes in the structure, operation, and management of the plant made in the past. The knowledge of these developments is very important, mainly from the acceptability and integrity of information (data) for the new IS point of view. The decision about acceptance of the old information for the actual IS of plants should be taken in cooperation with the management of the plant. Rules for transformation of old documents and maps, as well as rules for the design, creation, operation, and maintenance of the new IS, are formulated and defined by the IS project (design). The IS design defines the basic structure (conceptual model) of the IS and software tools which are appropriate for development, management, as well as operation of the IS.  The decision about tools should be taken from the point of view of the actual professional development in this field, the current state defined in standards, needs, and requirements of the management of the plant as well as the current legislation in the country. The IS should provide information for all units and departments (sections) of the plant and eventually for the public, too. Structure and level of detail of the provided information should be defined for all units and are different according to the position and importance of the unit in the plant structure as well as its relation to the IS. The IS of the industrial plant should provide: • • • •

Visualization of objects of the industrial plant according to given parameters Visualization of data about all objects registered in the IS Access to data according to defined rights for all users Rules for the regular update and archiving of the IS database and components

3.4  Information Systems of Industrial Plants

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• Rules for creation, operation, and maintenance (update) of the factory base map, as well as maps, included to the IS. The IS includes information and data about parcels and buildings which are in the ownership of the plant, communications, railways, operation, and energy lines situated and installed in the plant or their operation area. The part of the IS builds the geodetic reference frame (points) and all surveying tasks and their results. It should be decided whether the IS should include information about the equipment installed inside buildings and operation halls or not. The level of detail (LOD) of the information registered in the IS is defined by the needs of the plant units (departments) according to property evidence, land management, investment, operation, and decision-making in case of an accident and its handling. ISs of industrial plants are usually created similarly to geographical IS as object-­ oriented IS, which means that all elements registered by the IS are separate objects to which are connected information about them. Both parts of the IS, the database and the digital factory base map, are connected to each other. The database of the IS is the descriptive part, which includes data and information about objects registered by the IS. For access to the database and any operation with data, appropriate software should be used, which enables the categorization of objects and the definition of the structure of registered data. Each object could be identified by: • • • • • • • •

Identification code Name of the item (syntax usually used in databases) Type of data Reference to the code table Maximum number of characters (badges) Reference to the object of the factory base map Reference to the object of the database Additional comment

The structure of database categories is defined by the IS project which reflects the generally used structure of IS categories as well as the requirements and needs of the plant (Table 3.2). The digital factory base map is the main component of the IS graphical part, which is created and operated using appropriate software (Fig. 3.4). The IS project (design) should define the topology of objects and their relation to the database. The daily use and maintenance of the map ensure frequent access to objects, creation (drawing) of new components, etc. To make this more efficient, special tools may be developed and implemented into the software, which enables automated creation (drawing) of objects frequently occurring on the map. To make the visualization of the map or its selected parts more simply for the user, appropriate tools could be implemented, too. The reference frame of the base map is created by reference points connected to the national reference frame. In the case of the existing reference system of the plant (their own reference system – usually in the case of old plants), the exact transformation between both frames should be defined. According to the digital form of the

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3  Maps and Information Systems of Industrial Plants

Table 3.2  An example of categories of the industrial plant IS Name of the category D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn D_nnn

Description Roads, footways, compact surfaces, traffic signs Railways and their components Reference points, setting out networks, control points, etc. Structures with roof – buildings, halls, etc. Structures without roof connected with the ground Technology, equipment outside halls and buildings Bridge structures of operation lines and pipes Lines – water, canalization, other water pipes Lines – water for personal use, circulation water, etc. Lines – electricity Lines – steam and other operation lines Lines – gas natural Monitoring and signalization Geology, underground monitoring, wells Parcels Buildings registered by cadastre Housing and administration registered by cadastre Allowances for construction Integrated allowances Building approvals Surveying works Surveying plans for cadastre Statements and expressions of line operators Evidence of earthworks

base map, we do not define the scale of the map, but the LOD as is standardized in the field of geographical ISs. The content of the map is defined by rules for the creation of the factory base map as well as the needs and requirements of the plant management. All this information is collected in the given area of interest, defined by factory borders. In some cases, outside of the operation field (area) of the plant are additional areas where pumps, storages, water reservoirs, etc. are installed. These belong to the area of interest and are included in the factory base map and the IS, too (Fig. 3.5). The graphical content of the map is created by using the usual standards for drawing symbols (map keys). According to the needs of the units of the plant, also special additional symbols may be created and used. The IS project defines also the set of used colors, type, and size of text symbols, characters, etc. (Fig. 3.6). The map content is classified into folders, which are defined by the IS project, too. One folder is reserved for the cadastral map, as well as for the orthophoto map covering the area of interest.

3.4  Information Systems of Industrial Plants

Fig. 3.4  Example of the digital factory base map of an industrial plant

Fig. 3.5  Area of interest of an industrial plant

41

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3  Maps and Information Systems of Industrial Plants

Fig. 3.6  Symbols (characters) of the digital factory base map

The digital factory base map is usually saved and operated on the given server, where the whole IS (including the database) is installed. Maintenance and actualization of the map are made using remote access by personnel with appropriate knowledge and skills and access rights which allow them to change the map content. The actualization of the map content may be done on different levels, depending on the level of significance on the plant operation and safety. This will be given by the IS project in cooperation with the plant management. To ensure the safe operation of the base map, as well as the whole IS, it is desirable to archive the IS regularly and appropriately.

Chapter 4

Geodetic Networks of Industrial Equipment and Plants

Construction of large investments usually requires a setup of a local geodetic network, which is above the national geodetic networks according to their density, as well as accuracy. Local geodetic networks are built for limited areas for the setting-­ out and deformation measurement of civil engineering structures or structures of large demand (highways, tunnels, underground traffic lines, power plants, large industrial plants, technology complexes, etc.). The chapter starts with a description of local networks of industrial plants – their configuration, design, measurement, and the methodology of data processing. The special type of industrial networks is the micro-network, which is used generally for setting-out and control of industrial equipment. Micro-networks are small networks according to their geometry (configuration) but with very high-accuracy requirements. These requirements could not be fulfilled without special instrumentation and specific measurement methodology. The topic is discussed in his complexity including the data processing.

4.1  Local Geodetic Networks of Industrial Plants Construction of large investments with a large area occupation and challenging technical solutions usually requires a setup of own local geodetic network, which are above the national geodetic networks according to their density, as well as accuracy. Local geodetic networks are built usually for limited areas for the setting-out and deformation measurement of civil engineering structures or structures of large demand (highways, tunnels, underground traffic lines, power plants, large industrial plants, technology complexes, etc.). Local geodetic networks are consistent and homogenous in their whole configuration. Criteria used generally for classification of local geodetic networks are mainly the aim, area, configuration, density, and in some cases the methodology of their measurement. According to the aim of the network, we distinguish geodetic

© Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_4

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4  Geodetic Networks of Industrial Equipment and Plants

networks of cities, line structures, and networks for construction, montage, and operation of industrial and engineering structures. According to the configuration (shape) of the network, we divide them into linear-­shaped or areal (planar) networks. Linear-shaped networks may have a form of a line (alignment), polygonal structure, triangle, or quadrangle chain. Planar networks are built by triangle or quadrangle structures, in special cases by rectangular structures. According to the area covered by the network, these could be: • 5–20 km • 0.5–5 km • 5–500 m. Networks of the last category are known as micro-networks. To this category belong also mechanical engineering micro-networks, which are usually limited by the length of the measured distance by 5–50 m. These are used for measurement, assembly, control, or rectification of mechanical engineering equipment of high accuracy. According to their parameters (quality), they enable: • Determination of 3D relation of mechanical engineering equipment in general position • Use of analytical solutions in different coordinate systems (datums) • Use of adjustment calculus or the error theory and data processing to achieve optimal results During the assembly (montage), different technology equipment and engineering structures usually determine different tolerances of components, which are sent to the assembly as separate elements. The verification of geometry of these components or determination of their deviations from the design may be done very quickly, using geodetic methods, which enable determination of the 3D position of structure’s characteristic points. This kind of measurement is usually based on the existing micro-network. Local geodetic networks of industrial plants create a special group of geodetic networks, which are built with the aim to prepare a homogenous and accurate geodetic frame for all activities connected with construction and operation of industrial plants, as well as the setting-out and the control of the equipment. The size of the network is determined by the size of a plant and its part located outside. According to the kind of production and the installed equipment, the geodetic network can cover the area of size from 1 to 20 km2. To cover the area of this size with a network of points with a distance between them no larger than 200 m, it is necessary to have 200 points. In the case of local networks of industrial plants, planar, and vertical network, component is built separately. The shape of the planar component is determined by the shape and size of the area of the plant. The network’s structure is given by requirements of the high homogeneity and accuracy. Due to this, the network is built by triangle or quadrangle structures. In the 1960s of the last century, local networks for industrial plants were built with a rectangular structure (Fig. 4.1). In the case of this type of

4.1  Local Geodetic Networks of Industrial Plants

45

Fig. 4.1  Geodetic network with a rectangular structure

network, the shape of the network’s inside structure creates a very good assumption for the achievement of a high level of homogeneity of the network. The use of rectangular structure was given mainly by the requirement of high accuracy, the absenting EDMs that time and the setting-out of the plant using rectangular coordinates. In case of use of polygonal structures for the network densification or for the creation of the structures on the network border, it is necessary to ensure enough redundant measured values (Fig. 4.2). Except for the large level of homogeneity, another benefit of networks with a rectangular structure is the simple and quick repair of network points. Disadvantages are time-consuming setting-out of network points, their position in the center of crossings, which is connected with increased risk of the measuring personnel. Points are installed by using nails built in the compact road surface in small shafts with hood (Fig. 4.3). In the past, classical (terrestrial) methods were used for measurement of networks. Nowadays’ instruments and equipment enable the use of a broad spectrum of methods. The application of the particular method is limited by special conditions typical for industrial plants. Mainly the use of GNSS technology may be significantly limited in density and the structure of objects, because of a large number of steel structures producing multipath effects. On the other side, the possibility to determine distance with high-relative accuracy enables the increase of accuracy of the determined network parameters. According to this, the GNSS technology is appropriate for the determination of the relation between local and national geodetic networks. The local reference frame (coordinate system) of industrial plants is usually derived from the main axes of a plant, which are often connected to axes of main communication lines or main equipment. Parallel displacement of reference frame

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4  Geodetic Networks of Industrial Equipment and Plants

Fig. 4.2  Completing the network by polygonal structures in the border area Fig. 4.3  Stabilization of points using nails installed in a shaft

axes is often used to have the whole area of a plant in one quadrant. Usually, we use a planar, rectangular coordinate system with the clockwise orientation of axes, often without the exact definition of the reference plane position. According to the usual size of a plant and the required accuracy of measured parameters, the absence of this information is not critical from the geodetic measurements point of view. However, this should be solved before the relation (transformation) between the local and national network will be defined. For data processing, we use known methods of mathematical statistic and error theory. By measuring the whole network’s structure, data processing will use a large number of redundant measurements and between the measured values will be strong relations, which will reflect the network structure. This, together with the equal quality of measured values (angles and distances), ensures high quality and homogeneity of network parameters. That kind of structure of measuring values enables good control of systematic influence in measuring values and elimination of this influence during data processing.

4.2  Geodetic Micro-Networks of Industrial Plants

47

The required accuracy of the determination of network points results from the setting-out accuracy of civil engineering structures, communications, and lines in a plant. The highest-accuracy requirements are formulated by railways, their setting-­ out (local rails, balances, yards, etc.), which designed traffic velocity is limited by 20 km/h. Increased accuracy requirements are given when mechanical connection or connection for transportation is built between objects of a plant. In such cases, limits are created not by geometry (shape) of objects but by the relation between them. The high-accuracy requirements of setting-out and control measurements of equipment are solved by networks of small size, especially and separately built inside of these objects – micro-networks (see Sect. 4.2). Points of local networks for height measurement are usually stabilized by standard benchmarks in the basement of civil engineering structures. Choice of the reference frame of a plant is often determined by the era of the plant foundation, and so, today’s plants still used height reference reflecting the situation at that time. Height differences between points are measured by leveling, using closed loop, or leveling between two given points. Generally, the method and instrumentation of precise leveling had is being used. Data are processed by a method, which applies the well-known method of a less square method (LSM) and error theory. The network structure and a big number of redundant measurements enable detection and effective elimination of systematic influences as well as achievement of high accuracy.

4.2  Geodetic Micro-Networks of Industrial Plants Geodetic micro-networks used in mechanical engineering are the base of setting-out of different engineering technology and equipment (rolling mills, rotary kilns, generators, crane runways, etc.). Micro-networks may be used parallel as a reference network for control of structures and equipment during their montage, after general repair as well as rectification. They are also used for long-term control of structures during the operation to prevent possible operation breaks and ensure the safety of their operation. A small size of these networks (distances of 5–50  m) and high-­ accuracy requirements bring more particularities, which should be taken into account during measurement and determination of their parameters. The required accuracy of micro-networks is given for both their size and shape (form). The required accuracy of a network shape could be ensured by high accuracy of angle measurement. Accuracy of the network’s size is the function of distances measured in the network. Micro-networks could be classified according to standard deviation of the measured distances: • • • •

First class σs = 0.001 mm Second class σs = 0.01 mm Third class σs = 0.1 mm Fourth class σs = 0.5–1.0 mm.

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4  Geodetic Networks of Industrial Equipment and Plants

Geodetic methods and measurement could be used for the fourth and the third class. This level of accuracy requires special actions mainly for the stabilization of network points, as well as the use of dependent centration of instruments and targets. The shape and configuration of a network are determined by the geometry of a measured engineering object or equipment. Networks of column-shaped objects (reactors, chimneys, cooling towers, etc.) will have different shapes than networks of line-shaped objects (rolling mills, montage lines, etc.) or networks for measurement of crane runways (Fig. 4.4). According to the required accuracy of micro-networks, it is very important to ensure the correct centration of instruments and targets. The measurement without dependent or forced centration of instrument and target is not possible. In the case of dependent centration, we use tripods with tribrachs, which are closely centered and leveled before the measurement, and their position remains the same during the measurement (not changed). In case of forced centration, measuring pillars on all points of the network is built. They are equipped with centration tops. These could be: • Opening for centration crew (Fig. 4.5a) • Opening for centration bulb (Fig. 4.5b) When the centration bulb is used, on the top of the centration plates are made striae, which help to eliminate possible movement of the instrument installed on a plate. Leveling screws of the instrument should be adopted to this setup (Fig. 4.5c). The centration plate should be horizontal to ensure the vertical setup of the opening ax in line with the instrument’s vertical ax. When the plate is not in a horizontal position, the eccentric setup of an instrument and the target will occur. The eccentricity is in functional relation with the height of an instrument or target center point

Fig. 4.4  Different structures of geodetic micro-networks

4.2  Geodetic Micro-Networks of Industrial Plants

49

Fig. 4.5  Centration plates. (a) With an opening for centration screw, (b) with an opening for centration bulb, (c) centration plate with striae

Fig. 4.6  The eccentricity caused by an inclined centration plate

above the plate (Fig. 4.6). The inclination of the centration plate α = 10′ and the height of the instrument (target) center above the centration bulb center h = 250 mm will cause an eccentricity of e = 0.73 mm. This value is significant according to the usual standard deviation of micro-network points. The impact of this eccentricity on measurements could be reduced by calculation and application of corrections. The impact of eccentricity could be minimalized using special targets developed for the measurement of engineering structures (applications), which have a minimum height above the centration plate. For their centration special equipment is used (Fig. 4.7). In the case when classical prism and targets are used is important to apply high-­ quality targets, which centration accuracy is better than 0.5 mm (Table 4.1). In the case of repeated measurement, the impact of the eccentric setup could be minimized by the orientation of tribrachs on the pillar same way in each epoch. To ensure this, on the centration plate of each point is marked the position of a tribrach during the first measurement. During the following measurements, the tribrachs are

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4  Geodetic Networks of Industrial Equipment and Plants

Fig. 4.7  Targets for mechanical engineering applications (Hexagon 2019) Table 4.1  Centration accuracy of targets (Leica Geosystems 2009)

Prism type Material Centration accuracy

GPH1P Metal 0.3 mm

GPR121 Metal 1.0 mm

GPR1 Plastic 2.0 mm

Mini GMP101 Metal 1.0 mm

GRZ122 Metal 2.0 mm

GMP111 Metal 2.0 mm

oriented the same way. In some cases, setup of instrument in the same height (level) is required, which could be achieved by (1) marking the height of the instrument on a centration bulb (screw) or by (2) fixation of one of the leveling screws of the instrument and leveling the instrument using only two screws. The second approach requires good knowledge of the measuring personnel of this special practice. When the above-described approaches are applied, the eccentricity of instruments and targets during the repeated measurements will be of the same volume and direction, which results in the elimination of their impact on the measured values.

4.3  Measurement of Angles in Micro-Networks Measurement of angles belongs to the most important part of the micro-network creation. Throughout the measurement, we should take into account specific conditions that are fully different from the measurement of angles of classical geodetic networks. Distances of micro-networks are very short, and their length varies from 5 m up to 50 m. In some special cases, also shorter distances occur, up to 1 m. In that case, the minimum focusing distance of the used instrument should be checked before the measurement. The shortest distance that could be focused is usually

4.4  Measurement of Distances in Micro-Networks

51

between 0.6 and 1.0  m (e.g., Leica TM6100A has a minimum focusing distance 0.6  m). In case when measured distance is shorter as the instrument’s minimum distance, it is necessary to use additional lenses delivered by the producer of the equipment, on special request. Variated length of the line of sight leads to continuous focusing of the telescope during the measurement. Due to nonperfections in focusing lens setup inside the telescope, this generates small changes in the position of the telescope’s line of sight during the measurement. This could not be eliminated, only the impact on the angle measurement could be minimized. It is necessary to measure angles in two faces, in rounds (sets), or in laboratory units (a special method of angle measurement used in engineering survey). For measurement could be used only such instruments, of which axes fulfill the basic geometry requirements or the possible nonperfections in their position are small and known. The knowledge of the instrument’s basic condition enables the calculation and application of corrections during the data processing. In the case of measurement of micro-networks only instruments, which fulfill the basic condition at a required level, are used. This is checked by laboratory or field tests. The structure (configuration) of micro-networks is built overall by triangles and rectangles. According to this, it is necessary to make a check of closures and adjustment of angles according to the conditions given by the triangle or rectangle structures at the end of the measurement. Generally, we may accept the accuracy level of angle measurement described by the standard deviation from the interval of σα = 0.1 to 0.3 mgon, which occurs of the lateral deviation of 0.2 mm at a distance of 50 m (Table 4.2). To achieve this high accuracy, it is necessary to measure angles in rounds or in laboratory units.

4.4  Measurement of Distances in Micro-Networks According to the required accuracy of the distance measurement as well as special conditions during the measurement, distances in micro-networks could be measured using: • • • •

Compared steel or invar tapes with a millimeter scale Invar wires Parallactic method Electro-optic distance measurement with σd max = 0.5 to 1.0 mm

Table 4.2  Lateral deviations in relation to the angle measurement accuracy Lateral deviation at distance Relative error Accuracy class Standard deviation of angles [mgon] 5 m [mm] 50 m [mm] First class 0.1 0.008 0.078 1/640,000 0.3 0.024 0.236 1/210,000

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• Interferometry with σd max = 0.05 to 0.10 mm • Non-direct measurement In the case of non-direct measurement, the measured distance is determined by angle measurement of the given structure, which includes the baseline built by the leveling rod or substance bar in the horizontal position. The measurement of distances by tapes in micro-networks ensures the acceptation of all requirements (principles) of the tape measurement – the tape position, tightening, and others. For measurement should be on principle fused only those tapes and equipment, which ensure the accuracy of 0.1–0.5 mm. Scaling on the tape should be made with the required quality of 0.6 mm/1 m. If a scale of the tape cannot ensure the given accuracy, it should be calibrated to determine the correction for each possible reading on the tape. To determine the correct values of measured distances, we should apply the correction of the tape length due to temperature changes. The temperature of tape should be measured with an accuracy of 0.2 °C. Coefficient of the tape tension may be determined according to the tape’s material by: • Steel: α = (1.0 to 1.2)·10−5 °C–1 • Rustless steel: α = 1.0·10−5 °C–1 • Invar: α = 1.2·10−6 °C–1. The correction may be calculated using the equation:

∆d = d ( t − t0 ) α .



(4.1)

Tightening of the tape is very important; this should be applied with the same force, as was applied by its calibration. When this could not be ensured, the force applied during the measurement should be marked and the measured distance corrected by ∆d = d

( F − F0 )



Eq

(4.2)

where F is the force applied during the measurement. F0 is the force applied during tape calibration. E is the tape elasticity coefficient related to the material of a tape. q is the volume of the cross-section of the tape. If the tape is not tightened with required force, it causes tape’s sag and the measured distance should be corrected by



∆d = d 3

Q2 24 F 2

where Q is the mass (weight) of 1 m length tape (ca 0.03 kg).

(4.3)

4.4  Measurement of Distances in Micro-Networks

53

Lengths measured with higher accuracy may be measured by using invar tapes or wires, which are produced from invar with a scaling of every 100 mm. Each division is marked on a tape with a small hole in which a special scale of length 100 mm is mounted and equipped by Fennel’s microscopes. Using microscopes and tightening of a 20 m length tape in laboratory conditions, the accuracy of 0.02 mm may be achieved. If the reading will be done using a magnifier and the tape will be tightened by a given force, in industrial surroundings, it could be achieved a standard deviation of a measured length of 0.1 mm. The parallactic method is well-known. In the case of short distances and special maintenance during the measurement, this method could be used for the fourth or eventually third class. The successful use of this method depends on the accuracy of the measurement of the parallactic angle with the standard deviation of σδ ≤ 0.2 mgon. The length of distances between network points should not exceed 20 m. Distances of longer than 20 m should be divided into two separate parts. In the case of parallactic measurement in industrial surroundings and higher accuracy, a special substance bar with more targets is used (Fig. 4.8). The use of this kind of bar enables determination of the measured length by redundant measurements and parallel with determination of the distance we may determine the bar eccentricity and its incorrect orientation. The bar is from a very stable material and consists of one component (without mechanic connection), which leads to very high accuracy in the determination of their nominal length. The use of instruments for electro-optic distance measurement (EDM) enables to achieve a standard deviation of the measured distance of σd  =  0.5 to 1.0  mm. According to specific requirements, the group of EDMs able to ensure this accuracy is very small (Table  4.3). Producers mark this type of EDM in their catalogs as industrial equipment and offer much additional equipment (for exact centering of the instrument and targets, special reflecting prisms, foils, etc.), which help to meet accuracy requirements in real conditions.

Fig. 4.8  Substance bar with more targets (Kopáčik 1998)

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Table 4.3  Industrial total stations and theodolites currently on the market Type Sokkia NET05AX Leica TDRA6000 Leica TM6100A

Producer Sokkia Leica Geosystems Leica Geosystems

Accuracy of the measured distance 0.5 mm + 1 ppm

Accuracy of the measured angle 0.15 mgon

0.5 mm + 1 ppm

0.15 mgon

–

0.15 mgon

Table 4.4  Accuracy characteristics of chosen mobile interferometers and laser trackers Type Producer FARO FARO Vantage Leica AT960 Leica Geosystems Radian API Radian

Accuracy of the measured distance 16 μm + 0.8 μm/m

Accuracy of the measured angle 20 μm + 5 μm/m

0.5 μm/m

15 μm + 6 μm/m

10 μm

3.5 μm

In the field of metrology, we use mobile interferometers and laser trackers for verification and testing coordinate measuring machines and similar instruments (systems). Use of these instruments for direct measurement is possible when the exact centering of an instrument, and prism is solved with sufficient accuracy. Using interferometers for direct measurement of distances may achieve the highest accuracy only in case when the stability of physical parameters of surrounding (temperature, humidity, and air pressure) is ensured parallelly. Variating conditions decrease the measurement accuracy by one order, but it will be still at the level of 0.01 mm (Table 4.4). Non-direct distance measurement consists of measurement of angles in a given structure (usually the Hansen’s quadrangle), in which one length is represented by a measure of known length (Fig. 4.9). For that aim are used substance bars or leveling rods in horizontal positions, of which nominal length is known with an accuracy of 0.01 mm. When angles inside the structure will be measured with an accuracy of 0.1 mgon, the standard deviation of the determined length will be 0.05 mm. From two possible shapes of the quadrangle, the shape with a parallel position of the bar (rod) is often used. In case of non-direct determination of distances, the basic principle of “from large to small” is not accepted, because in most cases the determined distance is larger than the base. This should be taken into account when the systematic impact of the determined (measured) distance on the micro-network size will be analyzed. Due to this, knowledge of the correct value of the base nominal length is important and required. The temperature of the bar (rod) should be registered and during the measurement should be used only a calibrated bar (rod). Accuracy of the micro-­ network size determination may be increased by measurement of two or more basis inside the network.

4.5  Design of the Accuracy of Micro-Networks

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Fig. 4.9  Non-direct measurement of distances by Hansen’s quadrangle

4.5  Design of the Accuracy of Micro-Networks When micro-networks are used for setting-out of structures, it is necessary to determine their parameters with the accuracy required for setting-out. To complete this requirement, it is necessary to measure the maximum number of possible values (distances and angles) and to determine the network’s parameters by adjustment. In case when the network is used only for check of the structure’s shape, it is enough to determine this according to these accuracy requirements. Due to high accuracy, demand also in the lowest accuracy class, facts, which usually are not applied during general geodetic measurements, should be taken into account during the design of the network accuracy. To this belongs, for example, the convergence of the gravity line. The convergence is very small, but in case of geodetic works for the third class mainly in distance measurement, it could be (significantly) measurable. For example, the convergence at two points with the distance of 50 m between them will be



δ=

ζd = 1.6′′ = 0.5mgon R (4.4)

where R is the middle Earth radius, R = 6380 km.

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4  Geodetic Networks of Industrial Equipment and Plants

Fig. 4.10  The impact of visible horizon

The difference between visible and the real horizon Δh will be determined by (Fig. 4.10)



∆h = d.tg

δ d2 . ≅ 2 2R

(4.5)

For d = 50 m, R = 6380 km will be Δh = 0.2 mm. For a priori accuracy analysis are applied well-known procedures of mathematical statistics. It starts with a priori characteristics of instrumentation used for measurement, for example, for Zeiss THEO010A will be the accuracy of simple targeting σc = 0.6 mgon and reading σ0 = 0.4 mgon. When the forced centering of the instrument and targets on pillars are used, also the analysis of the eccentric setup should be applied, according to relations described in Sect. 4.2. Finally, using the required standard deviations of the angle measurement, the number of rounds will be determined. The standard deviation of direction measured in “n” rounds is given by



σ α nsk =

σ c2 + σ o2 . 2n

(4.6)

4.5  Design of the Accuracy of Micro-Networks

57

The standard deviation of the zenith angle in “n” rounds will be



σ ζ nsk =

σ c2 + σ o2 + σ i2 . 2n

(4.7)

The standard deviation of the parallactic angle measured in one laboratory unit is σδ = 0.4 mgon. According to the standard deviation of the distance measured using the substance bar (l = 2 m) measured in “n,” laboratory units are given by the equation (ρ = 400.103/2π):

σd =

σδ d2

. lρ n

(4.8)

When the measurement of micro-networks is finished, we should check, whether the requirements were met. Accuracy of the angle measurement could be checked by calculation of the a posteriori value of standard deviation:

σα =

∑ vα vα , (4.9) n ( n − 1) ( s − 1)

where n is the number of rounds and s is the number of directions. Another way the accuracy of the angle measurement in the network could be evaluated is by calculation of closures U in all triangles and their testing by

U kr = σ kr tα s ,

where

tα = 2.

(4.10)

Using closures calculated could be the standard deviation of the measured direction calculated by



σα =

∑UU , 6n

(4.11)

where n is the number of triangles in the network. The accuracy requirements of zenith angles could be checked using closures of high differences calculated for each triangle or any closed structure in the network:

U hi , j ,k = di , j ⋅ cotgζ i,, j + d j , k ⋅ cotgζ j, , k + di , k ⋅ cotgζ i,, k .

This could be tested at the given tolerance or threshold level.



(4.12)

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References Hexagon. (2019). Leica Absolute Tracker. Theodolites and Laser Station Products. Product Catalogue, ver. 1.6. https://www.hexagonmi.com/cs-CZ/products/laser-tracker-systems/accessories-for-laser-tracker-systems/reflectors. Accessed 20 Dec 2019. Kopáčik, A. (1998). Meracie systémy v inžinierskej geodézii (1st ed.). Bratislava: Vydavateľstvo STU. Leica Geosystems. (2009). Surveying reflectors (White Paper). Characteristics and Influences. https://w3.leica-geosystems.com/downloads123/zz/accessory/accessories/white-tech-paper/ White%20Paper%20Surveying%20Reflectors_en.pdf. Accessed 20 Dec 2019.

Chapter 5

Special Methods for Measurement of Industrial Equipment

For setting-out and verification of the geometry of different equipment in industry surroundings could not be used every geodetic method, due to the required high accuracy or non-accessibility of measured components for the geodetic measurement. In these cases are necessary to use measurement technology, instruments, and equipment, which are able to ensure the required level of accuracy, usually of 0.01–0.001 mm. There are micrometric, electronic and optoelectronic instruments, and measuring equipment and systems developed especially for the control of geometry parameters of components of mechanical engineering technology.

5.1  Categorization of Methods Methods of measurement of geometry parameters in the industry (mechanical engineering) could be classified according to the relation between the measured value and the controlled parameters: • Methods of direct measurement • Methods of non-direct measurement When the direct measurement is applied, the searched dimension is determined using the appropriate measure directly, by their value or by a difference from the given (fix) value, realized by the used measure (micrometer, caliper, etc.). In the case of non-direct measurement, the applied measure determines other dimensions (values), which are later used for computation of the measured (determined) value. To methods of non-direct measurement belong, for example, the determination of the perimeter length by measurement of the diameter (radius) or the determination of the diameter by the measurement of the height of the arch or

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5  Special Methods for Measurement of Industrial Equipment

the substance, etc. According to the realization of measurement, the measurement methods could be classified to: • • • • •

Absolute (basic) Comparative Substitutional Difference Null method

In the case of the absolute method, the value of the measured parameter (dimension) is determined by reading on the scale of the used measure, caliper, tape, etc. When the comparative method is applied, the measured dimension (value) is determined as the difference between the measured value and the value realized by the measure. This functional principle use gauges, which are set up before the measurement to the given value. In the case of substitutional methods, the measured dimension (value) is substituted by the value of a similar type, known size, with the same reading (data) indicated by the instrument. The difference method is based on the determination of the small difference between the dimensions (values) of the same type and known size (value) and the measured value. In the case of the null method is the measured value determined from the balanced state held by one or more values of known size, which are in relation to the measured value. According to the art of the determination (quantification, registration) of the measured value are measurement methods classified into classes of: • Contact • Non-contact (contactless) methods During the contact measurement, the measure and the measured component are in contact. To this group belong the most of methods used in the industry. When the contactless measurement is applied, the measure is not in contact with the measured component. This enables to make the measurement during the production, without breaks. These methods are usually based on the application of electric and optoelectronic sensors. Each of the described methods has their own benefits, advantages, and disadvantages. It should be taken into account, that the different required accuracy takes different demands on the personnel which is responsible for the measurement. According to this, it is important to optimize the selection of the measuring method, to ensure the optimal results, to meet the required accuracy, and to minimize the costs. The selection of the method used for measurement is significantly affected by: • • • •

Type and size of the measured dimension (value) Time schedule of the measurement process Required accuracy Possible loading of the measured component

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61

• Repeatability of measurements • The level of possible noises • Accessibility and costs of instruments and the equipment used for measurement

5.2  Methods of Direct Measurement The uniformity of the measurement process of large dimensions (parameters) in mechanical engineering is ensured by the usage of the set of etalons. The main etalons used for measurement of lengths in the industry are the basic etalons. Different from the basic meter, where the nominal size is given by the distance between two lines marked on the prototype, the nominal size of basic etalons is given by the distance between faces (surfaces) of the etalon’s both ends, which are precisely machined. The etalons are measures with stable (fix) dimension (size). During their application, the required value (dimension) is realized with a combination of etalons of appropriate sizes. Basic etalons, determined for measurement of large sizes are usually produced in different alternative sets. These are produced from one piece of special steel, which should have the following properties: • • • • • •

Stability in size after hardening Hardness and resistance to abrasion Good machinability Good adhesion Constant coefficient of the temperature expansion Good corrosion resistance

Basic etalons of zero or first class are used for the control of precise measuring machines (with a resolution of 0.001  mm), second class etalons are used for the control of setup of precise equipment. Etalons of the third and fourth classes are used for other aims. Etalons are produced in sets, which differ by the number the size of pieces included (Fig. 5.1). In the case of measurement of large dimensions are the basic etalons connected by special connections. To make possible the usage of these connections, the etalons are equipped by opening at their ends. According to the geometry of the measured components (sizes) are known as measures for measurement of: • Inside dimensions • Outside dimensions To the group of measures for measurement of inside dimensions belong beside the basic etalons, calipers, gauges and slide gauges (Fig. 5.2), laser interferometers, and tapes. When the maximal accuracy should be achieved during the measurement of large inside dimensions in mechanical engineering, it is necessary to keep the correct technology of the measurement. To be able to set this kind of procedure, it is necessary to take into account all factors, which affect the measurement.

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5  Special Methods for Measurement of Industrial Equipment

Fig. 5.1  Gauge block accessory set – Johansson gauges

Fig. 5.2  Caliper with vernier

Critical is the accurate setup of the measure for the required measuring interval. The measures should be set up very carefully and before each measurement, because the setup could be of the measure could be violated during their usage. The setup or the check of the measure is made on precise measuring machines or other setting up equipment. The accuracy of this equipment and machines is crucial for the accuracy of measurement made by the measures. Due to high-accuracy requirements are these control measurements made in rooms (halls) with air condition. During the measurement should be registered the temperature of the measure as well as the temperature of the measured component. For this reason, they are used mostly as contact temperature sensors. The highest impact (influence) on the measurement in mechanical engineering is the temperature. According to this is important to make the precise measurements by 20 °C (if it is possible), to minimize the errors due to the thermal extension. If the temperature of the measure and the component are different, this causes errors which are proportionable to the temperature difference and the middle value of the thermal extension coefficient of the material of the measure and the component. In

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63

the case, when the temperature of the measure and the measured component is the same but different from the nominal temperature of 20 °C and the material of the measure and the component is different, occurs the temperature error, which is proportional to the difference in temperature (difference from 20 °C) and the difference in the thermal extension coefficient of the material of the measure and the component. According to this is important to make the measurement by the measure which is the same material as the measured component is. If this could not be realized, it is necessary to correct the measured values by this influence. To minimize this impact on the measurement and to minimize the value of necessary correction should be the measure prepared before the measurement on the place in times which is needed to equalize the temperatures of the measure and the measured components. In some cases could be shortened this time when the measure is placed on the component. The most often used measures for the measurement of inside dimensions are the calipers (compasses). They have a form of the bar at the end equipped with spherical measuring surfaces. Calipers are used for measurement of cylinder-shaped components or other geometric elements (shapes), for example, quadratic, elliptic form, etc. They are very small weight and their usage is very simple. Calipers are classified into groups: • Calipers without reading (fixed, with setup) • Calipers with reading Calipers without reading could be set up in the given interval to the required value. They should be controlled regularly to eliminate the possible error of the caliper setup violation. The setting up of the caliper to the required values is made by the setting up of both bars. In the final position are the bars fixed by screws. The most often reason of the caliper’s dimension violation is the random collision (contact) of the caliper with the component or other equipment of the measuring space or the drop of the caliper. Calipers with reading belong to the most often used measures of large dimensions (sizes) and are produced in a number of variations. Usually, they consist from the head with a micrometer of length 100–125 mm and different additions of the value of 25 mm, 50 mm, 100 mm, and 200 mm, which enable the measurement of dimensions from the interval of 100–500 mm. When the additions of length 300 mm or 500 mm are used, the measuring interval of the caliper will be extended up to 1300 mm. The disadvantage of these measures is the possible abrasion of the contact surfaces with their often usage, which results in the violation of the caliper’s nominal length. In the practice, came often to a situation, when should be measured the distance of two inside surfaces, but between them are any obstacles. In these cases are used calipers with circle-shaped (arch) brackets. Slide gauges for measurement of inside dimensions are usually produced with a measuring interval of up to 2000  mm. In special cases are constructed gauges, which maximal measurable value could achieve the 3500 mm. Gauges for measurement longer distances are not constructed due to their heaviness and forces needed for their operation (movement, shift).

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Fig. 5.3  Principle of interferometric length measurement

Interferometers represent the class of measures for direct measurement of distances with very high accuracy. The principle of the interferometric measurement of distances was defined by Albert A. Michelson in 1880 and is based on the interference of the transmitted and received signal (Fig. 5.3). The transmitted signal (1) is divided by the polarization equipment (semipermeable mirror) and directed to two lines (2) and (3), at the end of which are prisms. One of them is stable (2) and the second is shifted along the measured distance. The signals reflected by the prisms are split and interfering together (4) before their input to the detector. In the case, when are the phases of the signals the same, are their amplitudes magnified and in other cases are damped. According to this, they produce the image of variated light and dark paths (strips). Due to the prism shift are produced variated interference images, which describe the phase changes in the received signals. The measured distance is in relation to the wavelength λ and the number of lightpaths N



∆d =

λ.N . 2

(5.1)

Due to the characteristics of laser sources used for interferometer construction, mainly the short wavelength of λ = 633 nm, is the resolution of the measured distance of 1 nm. The actual value of the wavelength depends and variates according to the actual refraction index of the air, which the signal is crossing. Whereas this is in relation to the temperature, humidity, and the pressure of the air, the measured distance should be corrected. Most of the measuring instruments (systems) make this correction themselves, based on the values measured by the instrument or values set in the software before the measurement. The value of correction is significant and could variate between 10 and 20 nm according to the measured values. Measuring tapes are used in the field of mechanical engineering for measurements of the accuracy of 1 mm, in some cases of 0.1 mm. Only calibrated steel tapes could be used, and it is necessary to declare the tape calibration by the regular certificate of the calibration laboratory. The usage of tapes without calibration or tapes from other materials as steel and invar is not permitted. To the group of measures for measurement of outside dimensions belong calipers, gauges, and coordinate measuring machines (Fig. 5.4). These are usually able

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65

Fig. 5.4  Measures for measurement of inside and outside dimensions

Fig. 5.5  Micrometer caliper

to set up for the required dimension (value) in the given interval with the micrometric or cutting of device of the given length directly in the working place. The cutting device is setting up in the laboratory or another control station of the producer. The measure should be set up just before the measurement, always in the same position, and with the use of the same support which is used during the measurement. The operation caliper (gauge) is set up directly on the measuring station (place). When the measurement is finished, the setup is checked again. The measurement is realized in series, and the result is calculated as the mean value of the series. The measuring protocol should include the actual temperature of the measure and the measured component. According to the caliper’s shape are known arch-shaped (Fig. 5.5) and extended (Fig. 5.6) calipers. The arch-shaped calipers are used mainly for measurement components of cylindrical form of the maximal diameter of 2500 mm. The usage of the caliper for higher diameter values could be very large and heavy, which causes

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5  Special Methods for Measurement of Industrial Equipment

Fig. 5.6  Extended micrometer caliper

problems by their operation. Generally, the usage of large calipers requires the assistance of a minimum of three persons during the measurement. Extended calipers are more appropriate for the measurement of large dimensions up to 6000 mm. They could be limited by the position during the measurement and that is the reason, they could often apply for the dimensions near the top of the measured component. Calipers could be constructed with or without reading. Calipers without reading could be produced in the version of fix measure or the measure which could be set up for the given value (dimension). The micrometer or indicator head are the most often used calipers’ readings. The measuring interval of calipers with micrometer reading is usually 25 mm, opposite to this the measuring interval of calipers with indicator head is 10 mm, eventually could be extended to 25 mm or 50 mm. The disadvantage of calipers with micrometer reading is the possible changes (variations) in their dimension (nonstable dimension) during the measurement. The dimension changes are results of the caliper deformation due to the big measuring forces applied during the measurement. This disadvantage is not registered by calipers with indicator heads. Coordinate measuring machine (CMM) is a complex measuring system, which is able to measure 2D or 3D rectangular (Cartesian) coordinates in the plane or space. The measuring process and data processing could be fully automated. CMMs are produced in different structures and dimensions. CMMs have broad applications mainly in the field of mechanical engineering production of components and equipment. CMMs ensure the regular check of the production quality – mainly the geometry of components. The usage of classical methods for this control is often demanding and time-consuming and in many cases not enough accurate. The result of the CMMs application could be not only the deviations of the product geometry from the design but also the actual 3D model of the component that could be created. This kind of information is important for reverse engineering as well as the as-built documentation of products. More about the principle, the usage, and testing of CMMs could be found in Chap. 7.

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67

5.3  Methods of Non-direct Measurement Methods of non-direct measurement are applied for measurement of large dimensions (components) or for determination of the size and the adjustment (arrangement) of objects, equipment, and their components in the space. In the case of application of methods of non-direct measurement aren’t measured the determined value (size, dimension), but this is calculated using other values (dimensions) measured on the object (component), which measurement is usually more simple as the measurement of the searched dimension is. The accuracy of the determination of the searched dimension depends on the accuracy of the measured dimensions as well as the chosen method. In general, could be expressed using the Taylor’s law of error propagation. It should be taken into account, as bigger is the ratio of the measured and the searched dimension, as higher is the accuracy of the chosen method. According to the measured dimension which is used for the calculation of the searched dimension are known following methods of non-direct measurement: • Measurement using ancillary baselines (substance bar, leveling rod with invar scale in horizontal position, etc.) • Determination of parameters of cylinder-shaped objects (by measurement of the perimeter, arch length, the high of the arch, length of chords and the angle of their normal lines, the length of tangents and the angle of their normal lines, etc.) • Using measuring systems based on different physical principles The measurement of dimensions using ancillary baselines could be applied, for example, on the determination of the diameter of cylinder-shaped storages or structures. The measurement could be realized by the baseline in the centric position (Fig. 5.7). The parallactic angle δ and the angle of tangents β are determined by usual way. The searched diameter is calculated by:



Fig. 5.7  Determination of the cylinder diameter using the baseline in the centric position

d δ β = r = l.cot .sin , 2 2 2

(5.2)

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5  Special Methods for Measurement of Industrial Equipment

where l is the length of the baseline. δ is the parallactic angle. β is the angle of tangents lined from the instrument station to the measured surface. The advantage of this method is the possibility to measure the diameter without cranes and personnel. The measurement could be realized without operation breaks and are not needed special ancillary devices and equipment. In cases when the baseline could not be set in the centric position, the baseline could be applied in tangential position (Fig. 5.8). The diameter of the cylinder will be determined from: d =r = 2

δ β sin 2 2. β l − sin 2

l.cot



(5.3)

Next procedures apply the angle measurement at two stations (Fig.  5.9). The distance b between the instrument stations S1 and S2 will be determined by one of the methods of precise measurement of lengths and angles α and β are measured with targeting the tangential points of the measured surface (cylinder). The diameter d will be determined by the formula: d =r =b 2

α β − sin 2 2 β α sin − sin 2 2 sin

(5.4)

The third procedure for determination of the diameter of the cylinder-shaped object is based on the fixed baseline, along which is moved the telescope in the normal position (Fig. 5.10). The distance between the left and the right position of the telescope is the searched diameter d. The application of this method requires the special equipment for the telescope with the possibility of their movement along the baseline as well as the scale to make the reading which determines the telescopes

Fig. 5.8  Determination of the diameter using the baseline in tangential position

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69

Fig. 5.9 Diameter determination based on measurement of angles

Fig. 5.10 Diameter determination using baseline with sliding telescopes

position. Significant is the thermal stability of the baseline to ensure the correct determination of the diameter. The highest accuracy could be achieved using the first procedure when the baseline is in the centric position. The determination of the diameter by measurement of the chord is similar to the method of quadrants, which are used for setting-out of circles (arches). The procedure uses the length of the chord t measured by slide gauges and the height of the arch h (Fig. 5.11). The diameter d will be given by the formula:



d = 2r =

t2 + h. 4h

(5.5)

This method is appropriate for the measurement of the outside as well as inside dimensions of cylinder-shaped objects. The method of wrapping is based on the direct measurement of the object’s perimeter. This could be measured by regular or special steel tapes developed for this kind of measurement. Using this method is determined usually the diameter of objects which diameter is larger as 2000 mm. The tape should be forced by a constant force, which could be achieved by the usage of weights balance from 5 to 10  kg, according to the measured length. The ends of the tape are lined through

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Fig. 5.11 Diameter determination using the measurement of the chord

sheaves and the reading is made in the point which is common for both ends of the tape. The diameter is determined by the well-known formula:



d = 2r =

O , π

(5.6)

where O is the perimeter of the measured object (component). Tapes used for this measurement should be a few meters longer as the measured perimeter (e.g., when the searched diameter is d = 10 m, the perimeter will be O = 31,416 m).

5.4  Measurement Systems for Precise Tilt Measurement The measurement of the inclination (tilt) of industrial equipment belongs to the most important and required measurements. Measures, sensors, and measuring systems used for this kind of measurement using the principle of the non-direct measurement, where the measured inclination is determined by the relation between the angle of inclination and the measured value. This value represents the angle between the direction determined by the pendulum anchorage and the horizontal plane realized by liquid, which is measured by sensors working on different physical principles. The most often used and well-known systems are: • Sensors and instruments for inclination measurement (inclinometers, electronic levels) • Hydrostatic measuring systems • Pendulum measuring systems Electronic inclinometers and levels are used predominantly for measurement of the inclination of equipment. Hydrostatic and pendulum measuring systems are installed on large equipment complexes, for example, turbo-generators, reactors, dams of water reservoirs, etc. In the construction of inclination sensors, the physical principle of the pendulum is applied. According to the used transformation of the pendulum anchorage deviation from the balanced state, are known capacitance, inductive, piezoelectric, and

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71

resistance sensors. The most often used is the inductive principle, where the ­pendulum deviation from the balanced state is transformed to voltage using two coils (transformer principle) – Fig. 5.12. The sensor measuring range is limited by the distance between the twice of coils as well as the linear part of the transformation function – the function which transforms the output signal into the input voltage  – usually given by the interval of ±2.5 mm/m (Fig. 5.13). The resolution of these sensors is relatively high, and usually achieve the values of 0.001  mm/m. The used principle of transformation requires the thermal compensation of the measured values, which is often realized by the built-in compensation circuit. Inductive sensors have a small thermal drift which is significant during the first 2–4 min (depend on the sensor) and achieves the values of 0.020  mm/m. Due to this, in the case of repeated measurements, these sensors should be switch on during the whole time. The Leica NIVEL sensors use for the realization of the balanced state the liquid surface. Deviation from the balanced state is measured by the CCD sensor, which detects the position of the light spot and determines their deviation from the reference position (Fig.  5.14). The measuring range of the sensors could be chosen between 1.5 and 3.0  mm/m with the resolution of 0.001  mm/m. The producer describes the accuracy of the measured inclination according to the chosen range by values from 0.005 to 0.047  mm/m. The type NIVEL220 could be connected in series with other Leica sensors. Sensors, which use the principle of liquid balance, are often used in electronic compensators and electronic tube levels. These are usually built in other measuring instruments, equipment, and systems. Their accuracy is at the level of 0.01 mm/m, which is more appropriate for civil engineering applications.

Fig. 5.12  Talyvel inclination sensors (Taylor Hobson 2019)

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Fig. 5.13  LIBELA 2800 (Kyrinovič and Kopáčik 2005)

Fig. 5.14  Inclination sensors Leica NIVEL220

Hydrostatic measurement systems use the well-known principle of communicating vessels, according to the level of the liquid in the vessels in the balanced state are in line which is horizontal (Fig. 5.15). The balanced state describes the equation

p01 + ρ1h1 g = p02 + ρ2 h2 g = … = p0 n + ρ n hn g,

(5.7)

where p0n is the air pressure. ρn is the liquid’s specific mass. g is the gravity. hn is the liquid high in the vessel. To ensure the balanced state is necessary to achieve the equal air pressure and specific mass in each measuring point (vessel) and these should be constant (without changes) during the measurement. Due to this, hydrostatic measuring systems, which are used for precise measurements or for inclination measurement of special objects (industry, energy, research equipment), are constructed with closed vessels. In these systems, the pressure is held at the constant value using compressors operating in autonomous mode. The liquid’s specific mass could be changed during the

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73

Fig. 5.15  Functional principle of hydrostatic measuring systems

Fig. 5.16  Thermal corrections

system apply according to two reasons: (1) due to the long-term variations in the inside behavior of the liquid and (2) temperature variations in the liquid. Due to this is the system component installed at places with minimal temperature variations, and temperature sensors are installed inside the system. According to the registered temperature variations, corrections of the output signal are calculated (Fig. 5.16)

∆h = h0 γ ( t − t0 ) ,



(5.8)

where h0 is the high of the liquid level for the temperature t0. γ is the thermal extension of the liquid. t is the current temperature of the liquid. The crucial point of the hydrostatic system application is the determination of the liquid level in the vessel. To complete this task with the required accuracy different principles and sensors are used: • Float-gauge sensor

74

• • • •

5  Special Methods for Measurement of Industrial Equipment

Electromechanic sensor Capacitance sensor Ultrasound sensor Optical sensor

When the float-gauge sensor systems are used, the float-gauge is installed in each vessel. The float-gauge indicates the liquid level through the direct connection with the transducer which transforms the float-gauge movement into electric signal (voltage, capacitance, or resistance). The disadvantage of this construction is the smaller sensor stability due to the float-gauge movement on the liquid level. When the lining is applied to reduce the variations in the float-gauge movement in the horizontal plane, the friction occurs, which results in the later reaction of the system. The electromechanic sensor consists of the moving mechanisms with the stylus, which has a conductive connection with the electromotor which is responsible for the stylus movement (in the vertical direction). When the stylus connects, the liquid level the electromotor stops their movement, and the position of the stylus is registered. The high difference between the measuring points included in the system is calculated from the difference of the stylus position in the given vessels. The disadvantage of the usage of this type of sensor is the complex construction of the sensor mechanic as well as the delay in the breaking (stopping) the stylus movement, which generates systematic errors in results. As a disadvantage of the system should be appointed the variating time of measurement, also which depends on the measured high difference. Capacitance sensors use the principle of the variated capacitance due to the changes in the dielectric medium. In the vessels are installed capacitator’s plates, in a way that they are partly steeped in the liquid. The capacitator’s capacity is given by the sum of both the capacity of the part steeped in the liquid and the part with air as the dielectric medium. The actual capacity of each sensor in the balanced state is registered. Capacity changes (differences from the balanced state) registered during the measurement are in relation to the high differences searched. To disadvantages of this type of sensors belong the small (limited) range and small long-term changes in the sensor’s capacity, which are caused by a slow chemical reaction in the plates during the operation. Ultrasound sensors measure the distance between the sensor and the liquid level using the ultrasound distance meter. The disadvantage of this type of sensor is the lower accuracy due to the level variations as well as the long-term changes in the physical parameters of the liquid during the sensor operation. These changes (variations) resulting to variating conditions of the signal reflection, which finally results in changes in the measured distance. The optical sensors measure changes of the liquid level, based on the position change of the liquid/air borderline. The image of the borderline is registered by the CCD sensor that output signal represents the intensity of the light going through the vessel (Fig. 5.17). The appropriate data processing procedure determines the position of the inflex points in the output signal.

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Fig. 5.17  Light intensity changes on the liquid/air borderline

Fig. 5.18  System of optic elements producing the parallel beam of rays

To achieve the minimum deformation during the image processing is necessary to use light with a parallel beam of rays or to apply an optical system producing parallel light beams on their output (Fig.  5.18). The position of the inflex point could be calculated using the equation I = b+

a , 1 + exp ( c − h ) d 

(5.9)

where I is the light intensity. h is the vertical coordinate of the inflex point. a is the difference between the minimum and maximum intensity. b is the minimum intensity value. c is the position of the inflex point. d is the steepness (slope) of the lighting curve.

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5  Special Methods for Measurement of Industrial Equipment

The range of the hydrostatic measuring systems is limited by the vessel dimension – variates usually between 100 and 150 mm. The resolution of the determination of the liquid level is different according to the sensor type applied and could achieve a value of 1 μm. The accuracy of the measured high difference depends on the sensor’s resolution as well as the accuracy of corrections from the air pressure, temperature, and the liquid’s specific mass variations at each point (vessel), where the measurement is made. These achieve the value from 0.005 to 0.010 mm. The principle of the pendulum measuring systems is based on the measurement of the deviation pendulum hanging from the gravity direction in two directions, which are perpendicular to each other (Fig. 5.19). The value of the deviation is measured in the horizontal plane by linear sensors. According to the used mode of transformation of the inclination into the output signal are known: • • • •

Inductive sensors Capacitance sensors Resistance sensors Optical sensors

When the first three sensor type is used, it is necessary to apply thermal corrections, according to the difference in the air temperature during the sensor calibration and operation. There are usually implemented compensation circuits, which are able to correct the output signal during the operation of the sensor without the necessary input of the measuring personnel. In the case of inductive sensors, the pendulum hanging is lined between four coils. The input voltage signal of these is in relation to the changes in position (inclination). The range of inductive sensors is limited by the distance of the coils and variates up to 20 mm. When the length of the pendulum hanging is 1 m, the sensor Fig. 5.19  Principle of pendulum sensors

5.4 Measurement Systems for Precise Tilt Measurement

77

inclination range will be 20  mm/m. The resolution of these sensors is usually 0.02 mm/m, and the measurement accuracy is at the level of 0.1 mm/m. Higher accuracy could be achieved using capacitance sensors. In that case, the measuring range will be limited to 2 mm or 5 mm. The basic element of this kind of sensor is the capacitor, usually in the differential setup with the common plate in the middle (Fig. 5.20). The differential setup enables the achievement of the sensitivity two times higher, increased linearity of the transformation function as well as the compensation of the influence of the surrounding conditions. The pendulum hanging is connected to the capacitator’s middle plate, which movement of Δd occurs the change ΔC in the capacity of the differential capacitator



C = C1 + C2 , ∆C = C1 − C2 ,

∆C 2 ∆d . =− 2 C d − ∆d 2

(5.10)

To determinate, the pendulum deviation in both directions is necessary to use the twice of capacitors oriented (directed) perpendicularly. The accuracy of the deviation determination using the capacitance sensors could achieve a value of 0.01 mm/m. The biggest range, as well as the lowest accuracy level, is connected with resistive sensors. For the determination of the pendulum deviation usually, the linear type of these sensors is used. To determine the deviation in two directions is necessary to use the twice of these sensors, which are perpendicular to each other. Optical sensors are at least sensitive at temperature changes during the operation. The principle of these sensors is based on the capture of the image of the pendulum hanging using CCD sensors. The position of the pendulum hanging is detected through the shadow position on the image, which is measured (Fig. 5.21). The position (the coordinate) of the hanging could be determined, (1) as the mean value of the coordinates which belong to the twice of inflex points’ position or (2) as the middle of the abscissa, which defines the brightness of the shadow in the signal. The shadow brightness is in relation to the thickness of the hanging (wire) and the distance between the light source and the CCD sensor.

Fig. 5.20  Principle of the differential capacitor

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5  Special Methods for Measurement of Industrial Equipment

Fig. 5.21  Signal intensity registered by the CCD Fig. 5.22  Setup in case of two CCD sensor usage

Using two light sources will be two shadows projected at the same CCD sensor, which relative position includes the information about the position of the pendulum hanging in both directions (Fig. 5.22). In that case, is not necessary to use two CCD sensors and set these strictly perpendicular to each other. The range of the optical sensors is determined by the volume of the CCD sensor applied as well as the distance between the light sources, the pendulum, and the CCD sensor. With appropriate setup could achieve the range between 20 and 50 mm. The resolution is determined by the sensor geometry as well as the resolution of the used CCD sensor. Usually is possible to achieve the resolution of 0.1 μm. According to the measurement accuracy is given by 1 μm/m. Hydrostatic and pendulum systems based on optical sensors are used for monitoring of the given parameters and the stability of nuclear reactors and significant object in energy. Their application for long-term monitoring increases the level of

5.4 Measurement Systems for Precise Tilt Measurement

79

Fig. 5.23  Measuring system for reactor stability control

Fig. 5.24  Configuration of sensors on the reactor housing

safe operation of these objects. The usage of these systems enables the continual monitoring and registration with data processing in real-time as well as the fast visualization of the results for the operators. This is very important in the case of nuclear power plants (reactors), which monitoring using classical methods is possible during operation breaks, only. The reliability of results obtained by these systems is given by the parallel application of two different systems  – the hydrostatic and the pendulum system. For example, at the reactor housing and basement could be the system consists of three hydrostatic and two pendulum sensors connected to the computer through the A/D converter (Fig. 5.23). This setup enables the visualization of the results in real-time as well as the access to data and results from any point of the internal network of the power plant. The hydrostatic measuring system generates the relative high differences between the measuring points. To determine the reactor’s inclination should be calculated the plane defined by three sensors and in the second step the inclination of the plane, which is determined by the normal vector direction in space or by deviations of the normal vector from the direction of the gravity in the given point. The configuration of the sensors have to ensure the optimal conditions for data processing (Fig. 5.24).

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Table 5.1  Parameter of the hydrostatic and pendulum sensors installed Parameters Image

Hydrostatic sensors

Pendulum sensors

Measurement range Resolution Accuracy

10 mm

± 2 mm

1 μm 10 μm

0.1 μm 1 μm

Fig. 5.25  Digital and graphical presentation of the reactor position

The accuracy of the reactor inclination is the function of the accuracy of sensors (Table 5.1) used as well as their relative setup. The managing computer of the system could serve more sensors usually up to 32 hydrostatic and 32 pendulum sensors, it is necessary. The up-to-date position of the reactor is sent to the operator permanently in numerical and graphical form (Fig. 5.25).

References

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References Kyrinovič, P., & Kopáčik, A. (2005). Monitorovanie stavebného objektu snímačmi naklonenia. Acta Montanistica Slovaca, 10(2), 140–150. Taylor Hobson. (2019). Talyvel 6 and clinometers. https://www.taylor-hobson.com/-/media/ametektaylorhobson/files/product%20downloads/electronic%20levels%20and%20clinometers/ talyvel-6_clino_highres_en.pdf. Accessed 12 Dec 2019.

Chapter 6

Terrestrial Laser Scanning Systems

Laser scanning has become a part of the surveying practice during the last three decades of the development of scanning systems. Laser scanning technology is one of the most effective methods of spatial data acquisition and creation of 3D models in the present days. The advantage of the terrestrial laser scanning (TLS) to conventional geodetic methods is the effectiveness of spatial data acquisition. It is used more and more in surveying, civil engineering, industry, architecture, archeology, and in many other similar areas. TLS systems enable documentation of the whole measured object with all constructional elements. The high scanning speed of the current scanners enables a significant reduction of time necessary for measurement, an alternatively increasing amount of obtained information about the measured object. More data (several million points) enable creation of complex models or documentation of objects in the form of a detailed point cloud. The functional principle of the terrestrial laser scanning, testing and calibration of scanning systems, and basic principles of data processing obtained by TLS is described in the following chapters.

6.1  Functional Principle of TLS TLS enables the contactless determination of 3D coordinates of points located on the surface of the measured object. The scanning result is an irregular raster so-­ called point cloud, which documents the measured object. The point cloud is used as a base for the creation of a spatial model of the measured object or as a technical base for verification of geometrical parameters or for deformation analysis. TLS belongs among non-selective measuring methods; it means that measured points are located non-selectively in a raster, which is defined by regular angular distances in the horizontal and vertical direction. In contrast with conventional surveying methods, coordinates of characteristic points are obtained by modeling or by generalization of the main features of the created 3D models or the resulting point cloud (Fig. 6.1). For the effective use of TLS and data obtained by laser scanning, it © Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_6

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Fig. 6.1  The difference between the selective (left) and non-selective method (right)

is necessary to know the basic functional principles of these systems. Laser scanners as other measurement systems have their own physical, functional, as well as technological limitations, which have to be taken into the account during the preparation of measurement as well as during data processing. Otherwise, they can cause a devaluation of results even when the measurement was correct. Optical 3D measurement techniques use the method of triangulation or polar method to determine the spatial position, whereby they utilize characteristics of electromagnetic wave propagation in the environment. Systems using the triangulation principle can be passive, based on the processing of stereoscopic images or active using projection of various light marks and textures on the surface of the measured object. In the systems using the polar method, the measured distance is determined by impulse measurement (time-of-flight), phase measurement, frequency measurement, or interferometric measurement (Beraldin et  al. 2010). Classification of 3D optical measuring systems according to the determination of the spatial position of measured points is represented in Fig. 6.2. The position of a measured point, in the systems, using spatial triangulation, is determined on the base of image processing with known sensor geometry of the scanning system (Luhmann 2006). In most cases, these are active triangulation scanners where at the one end of a baseline a source of emission (light) is located, which projects light (measuring) marks or structured light on the surface of measured object and at the opposite end of the baseline, there is a camera (CCD, CMOS) scanning the position of the projected target. In most cases for creation of the 3D model of the measured object, it is necessary to signalize reference points on the surface of the measured object (to determine the interior and exterior orientation). Triangulation scanning systems have short range (up to 2  m in most cases) and higher accuracy about several hundredths of millimeters. Nowadays the majority of laser scanners with the range longer than 2 m use the principle of the spatial polar method. The 3D point position by these scanner ­systems is calculated from the measured horizontal direction (from a calculated horizontal angle ω), zenith angle ζ, and slope distance d (Fig. 6.3).

6.1  Functional Principle of TLS

85

Fig. 6.2  Classification of 3D optical measuring systems Fig. 6.3  Determination of a point position by the polar method

The position of the measured point (located on the surface of the measured object) is determined according to the following equations:



 X P   d ⋅ cos ω ⋅ sin ζ   Y  =  d ⋅ sin ω ⋅ sin ζ  .   P    Z P   d ⋅ cos ζ

(6.1)

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6.1.1  Distance Measurement Distance measurement in optical 3D measuring systems is realized by an electronic distance measuring device. The most used methods are the electro-optical indirect measurement, time-of-flight measurement, phase measurement, frequency measurement, or interferometric distance measurement. The electro-optical indirect distance measurement is used in those scanners which use the triangulation principle (optical triangulation). The triangulation laser consists of a base, at which ends a laser and CCD/CMOS sensor, catching the reflected laser beam, are located. In dependence on the distance of scanned object, the position of the laser beam spot changes on the image sensor. According to the position of the laser beam spot, the baseline and the parallactic (projection) angle, it is possible to calculate the distance of the object measured from the distance measuring instrument (rangefinder) or to calculate the coordinates of the measured point. Considering that the calculation is realized from a short baseline (the distance of the laser from the image sensor, eve. From the position of the image of the laser beam spot), its length has to be determined with high accuracy. Triangulation lasers are suitable for measurement of short distances because with the increasing distance, the uncertainty of its determination increasing too. Whereas at object distances in submeter range, they significantly dominate with accuracy over the scanners using the polar method; object distances from 2 m up to 10 m create a limit over which the electronic methods of distance measurements achieve higher accuracy (Beraldin et al. 2010). Scanners working on the principle of polar method use time-of-flight measurement, phase distance measurement, or frequency or interferometric distance measurement. The main parts of electronic instruments for distance measurements are transmitter and receiver. The electromagnetic waves are emitted by the transmitter, reflected off the surface of the measured object, and received the receiver. Time-of-flight distance measurement is based on the principle of transit time (time-of-flight) measurement, which is necessary for transfer the electromagnetic impulse (measuring impulse) from the transmitter into the receiver (to pass the double of the measured distance) (Fig. 6.4). The transmitter of the instrument transmits an impulse, which starts the measurement of transit time. After the reflection from the measured object, the receiver receives the measuring impulse and stops the transit time measurement. From the measured transit time t and from the known velocity of the impulse propagation in environment v the measured distance is determined as follows:



d=

v t , 2

(6.2)

while the velocity of the signal propagation in the environment is given by:



v=

c , n

(6.3)

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Fig. 6.4  Principle of time-of-flight measurement

where c is the speed of light in vacuum and n is the refractive index, which depends on air temperature, atmospheric pressure, and relative humidity. Phase distance measurement is based on the comparison of the transmitted and received measuring the signal. Modulated electromagnetic waves are used as a measuring signal with the wavelength λ. The transmitter transmits the modulated electromagnetic wave, it is reflected off the object and returns to the receiver, whereby a phase difference occurs between the transmitted and received wave. For any carrier wavelength, the measured distance is determined from the phase difference and the number of the whole waves (ambiguity) as follows:



d=

( N + ∆N ) ⋅ λ 2

,



(6.4)

where N is the number of the whole waves and ΔNis the rest defined by the phase shift Δφby:

∆N = ∆ϕ 2π .

(6.5)

Phase meters enable us to determine a phase shift only in the range from 0 to 2π that means it is necessary to know the measured distance with accuracy higher than λ/4. In order not to have to determine the approximate distance using other methods, modulated electromagnetic waves are used for the measurement, which can be amplitude modulated (AM) or frequency modulated (FM). Modulation of the carrier wave solves the problem with the determination of the number of the whole waves. Distance measuring instruments working on the base of the determination of phase shift use AM modulation of the measuring signal. By known frequency of modulation fm and velocity of signal propagation in the environment v, the measured distance can be calculated according to Smith (2015): d=

v ∆ϕ ⋅ 4π fm

(6.6)

In practice, it means that the carrier wave is amplitude modulated by several other modulating waves. The wavelength of the main modulating signal has to be

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longer than the double of the measured distance that means the maximum range of a phase rangefinder is defined by half of the wavelength of the main modulating signal. The resolution of the rangefinder then depends on the wavelength of the carrier wave (with the shortest wavelength). The atmospheric conditions, such as temperature, pressure, and humidity eventually chemical content of the environment, have an influence on the results of the electronic distance measurement. To eliminate these influences, it is necessary to realize correction (atmospheric correction) of the measured distance. That is in most cases realized automatically by the software of the distance measuring device. Most of the scanning systems with the range over 100 m enable to set these atmospheric corrections directly in the scanner’s software or these corrections are directly measured (calculated from the measured atmospheric conditions) by sensors embedded in the instrument. Two types of radiation sources are used in 3D optical measuring systems. The first radiation source is that one which generates noncoherent light (incandescent, luminescent, or sunlight). The second radiation source and also the most suitable radiation source of electromagnetic waves for scanning systems are lasers (Light Amplification by Stimulated Emission of Radiation). Laser radiation is highly monochromatic and has a narrow spectrum width in comparison with the other radiation sources. It is spatially coherent, intensive, and using an optical system highly directionally stable. Coherence allows one to create one bunch of laser beams with minimal divergence, thereby ensures a relatively small laser beam spot on the surface of the scanned object. From the physical point of view, the laser is an amplifier of electromagnetic radiation. The physical principle of the laser is based on the induced emission of radiation (photons) in the active environment of the laser. In the case of stimulated emission, the atomic electron transition is coordinated in a sense. One photon can trigger transitions related to radiation also in other atoms. Stimulated radiated photon has not only the same frequency as the photon which triggered this process but also the phase, polarization, and moving direction (Baník et  al. 2007). In laser diodes, these emitted photons move in an optical resonator, which is created by parallel mirrors with high reflectivity. When a photon passes around an excited particle, this particle is stimulated, and it radiates a photon of the same wavelength with the same moving direction as the original photon. Thus, the flow of photons increases, and when it passes through one of the mirrors, which is permeable or it has a small hole (elimination of diffraction is ensured using the optical system of lenses), these photons create a very intensive flow. The result is a coherent and low-­ divergent monochromatic bunch of light beams (Štroner et al. 2013). Lasers can be generally divided into three basic parts. The first part is an active environment, which contents atoms which are capable of excitation. The second part is created by the energy source, which triggers the excitation of particles. The third part is an optical resonator, which ensures the amplification of laser radiation (Fig. 6.5). The distance of the mirrors of the optical resonator has to correspond to the whole multiple of the half of the wavelength λ/2 to create an intensive stationary wave. Nowadays the semiconductor lasers are used in terrestrial laser scanners. The active environment of the semiconductor lasers is created by a semiconductor

6.1  Functional Principle of TLS

89

Fig. 6.5  Basic parts of a solid state laser

material, in which active parts are represented by electrons in a nonequilibrium state and by the holes (free carriers of charge). In comparison to the other lasers, the radiation transition in semiconductors is only between allowed energetic zones. The main advantage of semiconductor lasers is their compactness, low consumption of electricity, high effectiveness, small size, low sensibility by manipulation, the possibility of tuning in a wide spectral band, and according to the active laser environment also generating of radiation with various wavelengths. On the other hand, their disadvantage is the higher divergence of the generated radiation and the dependence of the generated radiation on the temperature of the semiconductor material. Particular attention should be paid to eye protection when using laser diodes. Laser scanners are mainly used in the normal environment around us, where the movement of people cannot be restricted, and it is also not possible to keep all safety precautions used in laboratory conditions. Lasers used in 3D optical measuring systems are designed and realized not to pose a security risk for user (land surveyor) and surrounding. According to the possible risk of optical radiation, lasers are divided into several safety classes from the least dangerous up to the most dangerous: 1, 1C, 1 M, 2, 2 M, 3R, 3B, and 4. Particular classes with their defined risk for eyes and skin are described in the standard IEC 60825–1: 2014 Safety of laser products. Part 1: Classification of equipment and requirements. Lasers of up to class 3R are used in laser scanners, which represent a low risk.

6.1.2  Projection Mechanisms for Laser Beam Deflection Laser scanning is a process by which 3D coordinates of measured points located on the surface of the measured object are determined. Measured points are located in a certain raster, which is defined by the user (land surveyor), alternatively by the

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control algorithm of the scanning system used. The raster of the points on the surface of the scanned object can be defined in three ways by: • Definition of the spacing of neighboring points of the raster in the horizontal and vertical direction for a certain distance between the measured object and TLS (e.g. 3 mm x 3 mm by 50 m) • Number of points per one rotation of the instrument (e.g., 40,960 points per 360°) • Angular spacing of the zenith angle Δζand horizontal angle Δωbetween neighboring points of the raster The deflection of the laser beam into the points of the raster is ensured by projection mechanisms, which are rotating or oscillating optical elements. The projection mechanisms have to be produced with high-geometric accuracy (flatness of the reflecting surface, the stability of the axis of rotation, etc.). Depending on the constructional principle of the scanner used, various principles of the deflection of the laser beam are used. One of the possibilities of laser beam deflection is deflection by an oscillating mirror. The laser beam is deflected in a plane, which intersects the object in the case of the leveled instrument (rotation axis of the mirror is approximately in horizontal position) approximately in a vertical profile (measured points are located in a vertical profile). By a combination of oscillating mirror and rotation of the instrument around its vertical axis, it is possible to scan the surrounding of the instrument, which is limited only in the vertical direction depending on the structure of the instrument and the oscillation of the mirror. The mentioned technique of the deflection is mainly used in hybrid scanning systems with a limited field of view of the instrument. An alternative is the use of two oscillating mirrors, by which it is possible to deflect the laser beam in two directions and to create a raster of points on the surface of the measured object. By this technique of deflection, the field of view of the instrument is limited in the horizontal and also vertical direction. It is therefore mainly used in camera scanning systems. The next possibility of deflection of the laser beam with a high rate is the use of rotating reflecting prism (or rotating polygon). The reflecting prism has a shape of a regular n-gon; its normal line passing through the center of gravity is also the axis of rotation. The beam is deflected by the prism in the vertical direction (in the case of a leveled instrument) and the measured points then create a vertical profile on the surface of the scanned object. In the present panoramic laser scanners, using the principle of the polar method, a rotating mirror, denoted also as a Palmer scan, is used as the projection mechanism (Baltavias 1999), (Wehr and Lohr 1999). The surface of the mirror and the axis of rotation enclose an angle of 45° by the present structure of the scanners. The beam from the laser diode falls onto the mirror surface under the same angle in the place where the axis of rotation intersects the surface. By this structure, the rotating mirror deflects the laser beam onto a circle perpendicular to the rotation axis of the mirror. The measured points then create a vertical profile (in the case of a leveled instrument) on the surface of the scanned object (Figure  6.6a). The field of view of the instrument in the vertical direction is then limited only in a

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Fig. 6.6  Deflection of the laser beam: (a) by a combination of two oscillating mirrors and (b) by a rotating mirror

minimal measure by the structure of the instrument (it is not possible to scan under the tripod or the base plate of the instrument). The deflection in the horizontal direction is ensured by the rotation of the scanner around its vertical axis. For deflection of the laser beam, we can use also a source rotating around two perpendicular axes to each other. This form is represented by robotic total stations with a scanning function. The scan rate is rapidly lower in comparison to laser scanners and is limited by the speed of servomotors or piezoelectric drive of the instrument and also by the speed of distance measurement and registration of the measured data. Another technique used for deflection of the laser beam is the deflection by optical fibers (fiber scanner). The rotating mirror reflects the laser beam into the optical fibers organized into a circle. The cylinder formed is rolled out into the plane so that the axes of the optical fibers enclose the required angle (divergence angle). The deflected laser beam creates a profile on the scanned surface while the distances between the profiles are defined by the speed of the vehicle on which the scanning system is installed. Photogrammetric scanning systems can use a static optical element. This optical element creates a vertical light plane in space. The scanned object rotates around the vertical axis, and the image of the created light profile is recorded by a camera (by a CCD or CMOS sensor). The model of the object is created by the connection of images of individual light profiles in a computer (Štroner et al. 2013).

6.1.3  Categorization of Laser Scanners Scanning systems could be categorized according to the various criteria. Depending on the placement, scanners are divided into terrestrial or airborne (aerial). If the scanner is placed on the Earth’s surface (or close to the Earth’s surface) or on a

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vehicle moving on the Earth’s surface (a car, a train, a robot arm, etc.), it is a terrestrial laser scanner. If the instrument is placed on an aerial vehicle (airplane, helicopter, UAV), it is an airborne laser scanning system. Terrestrial systems are further divided into static and kinematic, depending on whether they are placed stationary or on a moving vehicle (car, trolley, carriage, etc.). The most frequent realization of the kinematic laser scanning system is a so-­ called mobile mapping system located on vehicles (Fig. 6.7a) or a scanning system in a form of a railway track geometry measuring trolley (Fig.  6.7b). Kinematic systems placed on vehicles are used mainly for scanning of roads and their infrastructure and streets. Scanning trolleys are mainly used for documentation of rail corridors, railway track scanning including all equipment that belongs to the railway as well as for as-built documentation railway tunnels, etc. The next criterion for the categorization of laser scanners is the field of view and scanning range. According to that, scanners can be divided into cameras, panoramic, and hybrid scanners (Fig. 6.8). In the case of camera scanners, the laser beam is deflected (to points of a raster) by oscillating mirrors or prisms what enable the deflection of the laser beam into a relatively small field of view. Panoramic laser

Fig. 6.7  Kinematic terrestrial laser scanner systems: (a) Leica Pegasus mobile mapping system (Leica geosystems 2019) and (b) Amberg Rail Clearance IMS 5000 (Amber Technologies 2018)

Fig. 6.8  Categorization of TLS according to the field of view: (a) camera scanner, (b) panoramic scanner, and (c) hybrid scanner

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93

scanners use rotating prisms or rotating mirrors as projection mechanisms. The laser beam is deflected in the vertical direction only with minimal limitation (under the instrument), while the deflection in the horizontal direction is realized by the rotation of the scanner around its vertical axis. The hybrid system is a combination of the panoramic and camera scanner system. These scanners are able to scan 360° in the horizontal direction with a significantly limited field of view in the vertical direction. An oscillating mirror in combination with rotation around the vertical axis of the instrument is used as a projection mechanism. Another important property of scanners is the scan rate (speed of scanning) expressed by the number of measured points per second. Present scanners with short and middle range enable to measure several 100,000 points per a second (up to two million points per second). Scanners with long range have generally lower scan rate, which reaches several 10,000 up to 100,000 points per second. It is necessary to point out that the abovementioned classification of laser scanners is based on the present instruments offered which, however, develop over the time, therefore the categorization of the terrestrial laser scanning systems may change over the time (especially the scan rate of long-range instruments increases).

6.2  Measurement Using Terrestrial Laser Scanners The procedure of data acquisition and creation of models using TLS can be divided into three main steps. The first step is the preparation for measurement. It involves reconnaissance of the measured object, choosing stations for scanning, and signalization and, if necessary, determination of coordinates of reference points. The second step is the procedure of scanning (data acquisition). The third last step is the verification of the results in the field.

6.2.1  Preparation for Scanning During the reconnaissance, the surface and the shape of the scanned object and its structural elements are detected. Based on the information obtained about the object, the configuration of scanner stations and reference points are planned with respect to the type and characteristics of the scanner used such as range, the field of view, and accuracy. If it is not possible to scan the measured object from a single station, it is necessary to choose reference points in the scanning site. Reference points are used to join several different point clouds into one common coordinate system. They can be signalized naturally directly on the measured object (e.g., sharp edge, spherical shapes, or its parts), or they can be signalized artificially using targets. The majority of scanning systems use a particular type of target for reference points which are automatically recognized by the scanning system. They may be plane or spherical,

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alternatively hemispherical targets. After scanning of spherical targets, a sphere is fitted to the points lying on the surface of the target and its estimated center is used as a reference point. Other types of targets are plane targets with a retroreflective surface, which are recognized by the scanning system based on the high intensity of the reflected measuring signal or targets with high contrast between parts of the target (so-called checkerboard targets). In Fig. 6.9 there are some of the target types used for signalization of reference points – target Leica HDS (on the left), checkerboard target (in the middle), and spherical target (on the right). In many cases, it is necessary to create the 3D model of the measured objects in a given coordinate system (local coordinate system of the measured object or national coordinate system). The coordinates of selected reference points have to be determined in the given coordinate system by other conventional surveying methods. The results of scanning are transformed based on these points into the defined coordinate system using spatial transformation. Reference points have to be stabilized in a way that ensures their stability during the whole measurement. In the case of deformation measurements, in addition to respecting the principles of building a reference network, it is necessary to ensure their protection. For temporary stabilization of the reference points, magnets (Fig. 6.10) or tripods (if there is no metal element in the scanning site) are often used. An alternative are targets bonded by reversible adhesive tape or targets (especially checkerboard) in the form of self-adhesive papers (flat surface is needed). The most used form of permanent stabilization of reference points is a metal fastener (Fig. 6.11). An integral part of the preparation works is planning and implementation of occupational safety and health protection as well as the protection of instruments and equipment during the measurement. This is important mainly in industrial factories because the measurements are often realized during the full operation of objects. When choosing an instrument, it is necessary to consider the environmental conditions in which the measurements are realized, they can extremely differ from the conditions in other environments, e.g., urban areas. The instrument has to be

Fig. 6.9  Examples of targets

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95

Fig. 6.10  Temporary stabilization of reference points

often protected against extreme dust and humidity. Measurements are often realized in the chemically aggressive environment what significantly influences the form of stabilization of reference points (using a normal metal anchorage is not possible), or the measurements are realized in explosive conditions (instruments need certificate for explosive conditions).

6.2.2  Scanning Scanning means the procedure of the determination of spatial coordinates of points, which are lying on the surface of the measured object. It is also possible to obtain radiometric information (color) about the measured object during the scanning. This information is the intensity of the reflected measuring signal or colors (­ textures) from the images captured by digital cameras often embedded in the scanning system. Scanning consists of the definition of scanning parameters and of starting the scanning procedure. The scanning parameters define the area and the density of the scanned points on the surface of the scanned object. Laser scanners, which are equipped with a digital camera, enable us to define the scanning area directly on the digital image in the shape of a spherical rectangle. For most scanners, it is possible to define a scanning area also by starting and ending horizontal direction and zenith angle. The next important parameter is the scanning density (resolution) because this parameter influences the detail of measurement and consequently the amount of the data obtained by scanning. The resolution can be set by the definition of the angular difference between two consecutive points and profiles, it means by definition of the step for the horizontal and vertical angle Δω,Δζ, or by definition of raster parameters in a certain distance from the scanner, e.g., 3 mm × 3 mm per 50 m. To simplify the control of the instrument, some producers limited the possibility to set the scanning parameters only to define the scanning area and to choose the scan resolution from some predefined resolutions. The resolution in these systems is mainly defined as a number of points per 360° in the horizontal and vertical

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Fig. 6.11  Stabilization of reference points using self-adhesive paper (left) and using metal fastener in concrete (right)

direction, e.g., 40,960 points per 360°, which represents 1.5 mm x 1.5 mm per 10 m, eve. 7.7 mm × 7.7 mm per 50 m. After starting the measurement, scanning is performed automatically without any necessary intervention of the user. The scanning procedure is controlled by a control unit embedded in the instrument or by an external computer. The scanner determines the spatial coordinates of points and saves them into the internal memory of the instrument or into the control PC. In addition to coordinates, radiometric information is obtained during the measurement. This information is the intensity of the reflected measuring signal or color from the images captured by a digital camera. The measuring signal is reflected off the measured object with various intensities that depend on the physical characteristics of the scanned surface (material, color, roughness). On the base of the radiometric information, it is possible to assign a color to measured points (Fig. 6.12). The results of the scanning procedure are point clouds in coordinate systems of the scanner at particular stations and the abovementioned radiometric information. In some cases, it is suitable to complete the data from the scanner by digital images created by a high-quality external digital camera. These images are used for docu-

Fig. 6.12  Result of scanning – point cloud

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97

mentation of the measured object and are another source of information for processors and can be used for modeling or visualization of the results as a source of textures. Measurement using laser scanners is much easier at first sight in comparison with the conventional geodetic methods. During the measurement, it is not necessary to realize complicated and, in some cases, time-consuming identification of characteristic points of the measured object (especially in the case of industrial objects). The scanning itself consists of the definition of scanning parameters and of starting the measurement procedure. However, great emphasis should be placed on preparation works. The choice of the positions of the instrument, the reference points, and the overlap areas require careful reconnaissance of the measured object and its close surrounding. Care should be taken to ensure the stability of the reference points. Any change in their position is often detected only when the data is processed because the visual check of their stability during the scanning is practically impossible.

6.3  Processing of Data Obtained by TLS Processing of data obtained by terrestrial laser scanning often means creating a spatial model of the scanned object. However, in many cases, the creation of complex 3D models is not necessary. The result of data processing can be a modified point cloud, which sufficiently documents the measured object to the date of scanning. Such a modified point cloud is processed at any time when further information about the measured object is required and only in the necessary detail. In the case of deformation measurement, the result of the data processing is the direction and the size (magnitude) of displacement of the subset of the point cloud. Processing of data obtained by TLS is possible to divide into two main steps: • Adjustment of point clouds. It means the final modification of clouds and preparation of the results of scanning for processing. To this step belongs the cloud transformation (registration), removal of outliers (gross errors), removal of redundant points, filtration and data reduction, color assigning, and conversion into the required data structure (resulting file format). • Modeling and analysis. It includes the creation of the 3D model of the measured object or its parts. Data processing includes also analyses of results as, for instance, the determination of geometrical parameters of parts of the scanned object (dimensions, flatness, and others), volume determination, and modeling of various phenomena (flood water level and others). This step includes also analysis of deformations on the base of created models or on the base of the point cloud. Depending on requirements, data processing can involve also visualization of the results (adding textures and creation of animations of the created virtual model).

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6.3.1  Point Clouds Adjustment Before processing of scanned data, it is necessary to realize several modifications of point cloud. Above all, it means registration of point clouds into a common coordinate system, removal of incorrect and redundant data, elimination of reflections in the space between the scanned object and the scanner (people, transportation, dust, rain, etc.), and removal of the points, which are not necessary for data processing (all points which are not lying on the surface of the measured object). Furthermore, it means filtration and reduction of data, noise (data dispersion) reduction, reduction of the density (decimation) of point cloud, and conversion into the required data structure (creation of outputs in required file formats). The results of measurement are point clouds with coordinates in various coordinate systems (in the coordinate system of the instrument of the particular station). The registration can be divided into two steps. The first step is the adjustment of the transformation parameters, and the second is the transformation of the point cloud using the adjusted parameters. There are many algorithms for point cloud registration, which use identical points (reference points) or directly the points from a point cloud, which are in overlap areas (Štroner et al., 2013). According to the algorithm used, it is possible to distinguish three approaches for registration of point clouds (Lichti and Skaloud 2010) (Ge 2016): • Target-based registration. • Surface-based registration in the overlapping areas of point clouds. To this approaches belongs transformation using algorithm minimizing the sum of squares of distances between clouds ICP (Iterative Closest Point) or, for instance, transformation using algorithm minimizing the sum of squares of distances between two surfaces LS3D (Least Squares 3D matching). • Feature-based registration. Transformation on the base of elementary geometrical primitives obtained from the point cloud. For target-based registration, it is necessary to know the coordinates of identical reference points in both coordinate systems between which the transformation is realized. The coordinates of the reference points, signalized by artificial targets, are necessary to determine during the scanning of the measured object. Usually spatial congruent transformation is used for the registration (Fig. 6.13), since no change of scale between the coordinate systems is expected. In that case, six transformation parameters are determined: these are three translations of the origin of the coordinate system TX, TY, and TZ and three rotations around the axes of the coordinate system α, β, and γ. The transformation parameters are calculated using the following equation:

X = R⋅x + T

(6.7)

where X is the vector of coordinates of points in the resulting coordinate system (into which the points are transformed), x is the vector of coordinates of points in

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99

the transformed coordinate system (from which the points are transformed), R is orthogonal rotation matrix defining rotations around the coordinate system axes, and T is the vector of translations of the coordinate system’s origin along the axes (Fig. 6.13). To calculate the transformation parameters, it is necessary to know at least six coordinates of three noncollinear points (points which are not lying on the same line). In practice, it means that it is necessary to know the coordinates of at least three reference points (nine coordinates) or two reference points and the orientation of one coordinate axis. The most commonly used condition is the vertical direction of Z-axis, which is defined by the compensator embedded in the instrument. The advantage of surface-based registration approaches is that the transformation parameters are calculated only using the point cloud. It means that no reference points are necessary which simplifies the scanning procedure and reduces the time spent in the field. Another advantage is the higher accuracy of results in comparison with target-based registration. One of the first transformation algorithms proposed using minimizing the sum of the squares of Euclidean distances between the points of two point clouds is ICP (Iterative Closest Point) described in Besl and McKay (1992). The drawback of the ICP algorithm is its possible convergence to the local minima which may cause incorrect estimation of the transformation parameters. Because of this fact, it is necessary to divide the transformation into two steps. The first step is “an approximate” transformation (coarse registration), and the second one is “a precise” transformation (fine registration) (Wujanz 2016). The coarse registration is realized in processing software by manually selecting identical reference points (most often three reference points), based on which approximate transformation parameters are estimated. Subsequently, the fine registration is performed using ICP algorithm.

Fig. 6.13 Transformation parameters of the spatial congruent transformation

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The basic premise of the transformation using ICP algorithm is that the sum of squares of Euclidean distances between the nearest points (all i points in the overlap area) of two point clouds is minimized (Lichti and Skaloud 2010):



e2 = ∑R ⋅ x i + T − X i 2 → min i

(6.8)

In the case of feature-based registration, the transformation parameters are estimated on the base of the mathematical models of geometrical primitives such as planes, cylinders, spheres, or toruses. According to Rabbani et al. (2007), it is possible to distinguish between direct and indirect transformation methods. By the indirect transformation method, simple geometrical shapes are defined in point clouds, in which mathematical models are estimated using regression algorithms. The transformation parameters are then estimated by minimizing the sum of the squares of differences between the parameters of the mathematical models of particular geometrical shapes (e.g., identical cylinder in both point clouds). By the direct method, the parameters estimated by the indirect method are used as approximate values. The sum of squares of orthogonal distances between the points and their respective geometric features is minimized (e.g., the sum of squares of the orthogonal distances from a plane). The parameters of mathematical models of geometrical primitives and the transformation parameters are estimated in one step. The advantage of the feature-based registration is that, theoretically, no overlap between point clouds is necessary. It is enough if the modeled primitive appears in both point clouds (Lichti and Skaloud 2010). From a practical point of view, it is recommended to model the corresponding geometrical primitives from points lying on the same part of the surface to eliminate the errors from the imperfection of the geometrical shape of the modeled object (e.g., part of a pipe may not be an ideal cylinder). After the registration of point clouds into a common coordinate system, it is necessary to realize other modifications. These adjustments can be divided into the removal of the outliers, removal of the redundant points, assigning a color to the point cloud, reduction of data, and conversion of the data to the required file format. Depending on the scanning conditions, often are scanned also structures not related to the measured object (Fig. 6.14). These can be objects in the close surroundings of the scanned object, e.g., transportation (especially if the object is scanned from a long distance), but it can also be people, animals (birds), dust, or snowflakes (or raindrops). Point clouds can be colored according to the intensity of the reflected measuring signal. The measuring signal, depending on the physical characteristics of the scanned surface (color, material, roughness) and light conditions at the scan site, is reflected off the measured surface with various intensities. The value of intensity is described by a number, e.g., from 0 (the lowest) to 1 (the highest), and it is also described by a color scale, e.g., from red (the lowest) to green (the highest intensity). It is possible to color the points by real colors according to the digital images captured by the internal camera of the scanner or by an external digital camera (Fig. 6.15).

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Fig. 6.14  Point cloud of ship’s hull after registration (left) and point cloud after elimination of redundant points (right)

Fig. 6.15  Coloring of the point cloud according to the intensity of the reflected signal (left) and according to the digital images (right)

The coloring of point cloud enables the spatial perception of the scan data. By a monochromatic representation is too complicated for the user to perceive the geometry of the space correctly. The scan resolution is defined during the scanning procedure by the step of horizontal and vertical angle which means that the density of the resulting point cloud decreases with increasing distance between the instrument and the scanned object. Therefore, the result of the scanning is a point cloud with non-homogenous density. The non-homogeneity of the cloud is also increasing after the registration of point clouds, because in the overlap areas, the density of points is much higher than in the other parts of the measured object. A larger number of points also means a larger database and increased demands on the PC used for data processing. The number of points can be reduced by the decimation of points. The most software for data ­processing uses algorithms that allow “unifying” of the point clouds to increase the homogeneity of the density of points. After the realization of the abovementioned modifications, the point cloud documents the current state of the measured object without the necessity to create a 3D model. It is actually a virtual model in point representation. The database with the

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point cloud can be archived and later processed partially according to the requirements. Processing and creation of 3D models are performed in specialized software (in most cases developed by the producers of scanning systems). Most of the currently available CAD software has built-in tools for processing big databases of point clouds, in that case, the 3D models are created by known functions and tools of the CAD software. Laser scanners of various producers, as well as the data processing software, use various output file formats. The last step of point cloud processing is, therefore, the conversion into the required data format. Among the most used in ASCII text format belong: *.ptx (Leica), *.pts. (Leica), *.csv, *.txt, *.xyz. The most used binary file formats are: *.clr (Topcon), *.cl3 (Topcon), *.fls (Faro/ Trimble), *.fws (Faro/Trimble), *.ptg (Leica), *.zfs (Zoller&Fröhlich), *.rds (Riegl), *.rxp (Riegl), *.las (American Society of Photogrammetry and Remote Sensing), *.e57 (ASTM International), *.rcs (Autodesk), *.rcp (Autodesk). Files in binary format have a higher data compression rate, therefore the resulting file is several times smaller than ASCII text files.

6.3.2  Creation of 3D Models The results of laser scanning can be used as a geometrical base for various tasks. A point cloud obtained by TLS has the most universal usage from the data obtained by geodetic or photogrammetric methods. The point cloud can be processed as a whole or in parts as subsets of points. As a whole, the point cloud is processed when models of isolated objects or parts of objects are created. This is especially the case when a 3D model of the object is created using surfaces (e.g., sculptures, or digital terrain models) or when only a part of the object is scanned (e.g., determination of deformations of walls). Often the individual structural parts of the buildings or industrial objects have to be modeled separately. According to the algorithm used, it is possible to divide the methods for point cloud segmentation into five groups (Vosselman and Klein 2010), (Nguyen and Le 2013), (Grilli et al. 2017), and (Xu et al. 2018): • Edge-based methods – based on the detection of edges bounding different areas in the point cloud and subsequent segmentation of these areas. • Model-based methods  – using modeling of geometrical primitives and subsequent segmentation of points of these primitives (point lying on the surface of the primitive). • Surface-based methods or region-based methods  – for identification of points belonging to the same surface, they use a sequential selection of points with similar characteristics such are the orientation of the surface (normal), curvature, etc. • Clustering-based methods  – grouping points based on of their geometric or radiometric characteristics (e.g., point position, surface normal, and the intensity

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of measuring signal) or based on their spatial distribution (e.g., distance of the point from the center of cluster). • Graph-based methods – use graphs created from the point cloud, whose peaks are formed by the points of the cloud and the edges connect the points that meet certain criteria. The type of the 3D model and the procedure of its creation are chosen according to the character of the measured object, its geometrical characteristics (regular, irregular shapes), and according to the purpose of 3D model creation so that the results of processing allow further processing (e.g., various types of analyses, visualization, modeling of various phenomena, etc.). Modeling is often associated with point cloud segmentation, especially in the case of model-based segmentation. In general, it is possible to distinguish three main types of 3D models. The first one is a spatial model created by characteristic points of the modeled object and by spatial curves connecting these points, so-called wireframe model. The lines and curves of a wireframe model (Fig. 6.16) are the characteristic edges of the modeled object. The second type is a spatial model created by surfaces, so-called surface model. The surface model is possible to create by modeling of the surfaces of geometric primitives such as planes and various types of rotation surfaces (sphere, ellipsoid, cylinder, etc.) or by modeling of irregular surfaces (Fig. 6.17) using polygon meshes, triangulated irregular networks (TIN), Bezier surfaces (Ding and Davies 1987), B-spline surfaces (Boor 1978) or NURBS (Non-Uniform Rational B-Spline) surfaces (Piegl and Tiller 1995). The third type of 3D model is a solid or 3D model created by solids also known as volume models. There are two main approaches for the representation of volume models. The first one is boundary representation (B-rep.). In this case, the 3D model of the solid is created by surfaces bounding the solid. The second approach is the Constructive Solid Geometry (CSG) when the 3D model of the solid is created by Fig. 6.16 Wireframe model of a cube

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Fig. 6.17  B-spline surface

several geometric primitives using Boolean operations (union, difference, intersection, subtraction) (Fig. 6.18). In addition to the abovementioned approaches, a so-­ called sweeping and decomposition model can be used. In the case of the decomposition model, the 3D model of an object is created by small cells, most often by voxels, e.g., in the hierarchical arrangement of an octree (Mäntylä 1987). The creation of 3D models from point clouds is a procedure, in which subsets of the point cloud are replaced by one of the abovementioned types of 3D models to approximate the modeled part of the object as real as possible. According to the modeling, it is necessary to distinguish three procedures: approximation of the point clouds or their parts by surfaces of geometric primitives (plane, cylinder, sphere, etc.), and solids, modeling by lines and curves (creation of a wireframe model), and by irregular surfaces (meshes). In the case of the first approach, the point cloud or its subsets are replaced by simple mathematically defined geometric shapes. For instance, a wall can be approximated by a plane, columns and pipes can be approximated by a cylinder, etc. This processing method is used mainly for creating models of objects created by regular shapes (Fig. 6.19), e.g., buildings, mechanical, and industrial objects. Fig. 6.18  3D model created by Constructive Solid Geometry

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Fig. 6.19  Approximation of point cloud by a plane (up left), by a cylinder (right), and by a predefined beam (down left)

A simpler procedure is the creation of a wireframe model. Since TLS is a non-­ selective method, it is necessary to define the start and endpoint of the lines, generally the shape of the curves creating the wireframe model, in an appropriate way. Characteristic points of the edges of the modeled object are the points lying as close as possible to these edges. In the case of higher accuracy required, the wireframe model is created by regression curves fitted to the points in slices of the point cloud (Fig. 6.20). For processing the scan data, modeling by irregular surfaces can be also used (Fig. 6.21), mostly triangular meshes. This approach is similar to the approximation of the point cloud by geometric primitives. The difference is that the point cloud is

Fig. 6.20  Modeling by lines (modeling the edges of a window frame)

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Fig. 6.21  Mesh of micropile stabilization of a wall (left) and NURBS model of a ship’s stern (right)

approximated by a huge number of triangles (planes) while each of them is defined by three points of the point cloud. In addition to the triangulated networks, polygon surfaces, Bezier surfaces, B-spline surfaces, or NURBS surfaces can be also used for modeling of irregular surfaces.

6.4  Accuracy and Calibration of Terrestrial Laser Scanners To obtain reliable results, it is necessary to correctly identify and eliminate as much as possible errors affecting the results of laser scanning. As all measurements realized in a real physical environment, TLS is affected by random and systematic errors also. It is difficult to identify random errors, and it is almost impossible to eliminate them from the results of scanning. Most systematic errors can be ­identified using various testing procedures and by subsequent calibration of the instrument, their influence on the results can be minimized.

6.4.1  Source of Errors and their Mathematical Models Most of the present scanners operate on the principle of the spatial polar method (Fig. 6.3) therefore the a priori standard deviation of the spatial position of measured points can be calculated using the formula (6.1). By application of uncertainty propagation law and using the a priori standard deviation of measured values, it is possible to write the following formula for the standard deviation of spatial coordinates:

6.4  Accuracy and Calibration of Terrestrial Laser Scanners



σ XP =

( cos ω sin ζ )

σ YP =

( sin ω sin ζ )

σ ZP =

( cos ζ )

2

2

2

107

σ d2 + ( d ( − sin ω ) sin ζ ) σ d2 + ( d cos ω cos ζ ) σ ζ2 2

2

σ d2 + ( d cos ω sin ζ ) σ d2 + ( d sin ω cos ζ ) σ ζ2 2

2

σ d2 + ( d ( − sin ζ ) ) σ ζ2

(6.9)

2



where σ XP , σ YP , and σ Z P are standard deviations of coordinates of points P, σd is the standard deviation of the slope distance, σωand σζ are standard deviations of the horizontal and zenith angle. The standard deviation of the spatial position of the measured point, which characterizes the uncertainty in the position of the measured point is related to the “projection center” (the origin of the coordinate system) of the instrument then is calculated using the following formula:

σ XYZ P = σ X2 P + σ Y2P + σ Z2P .



(6.10)

Using the abovementioned formulas, it is possible to calculate the accuracy of the determination of the position of discrete measured points. To express the accuracy of the scan results, it is necessary to test the scanning systems (the software together with the hardware) as a whole from the results quality point of view. The systematic errors of laser scanning systems are divided into two main groups. The first group includes errors, which can be modeled by mathematic functions. These are mainly instrument errors, which are caused by the imperfection of the production of instruments and their parts. This category includes the additive constant and the scale error of electronic distance measurement (EDM) instrument, the eccentricity of the horizontal or vertical circle, collimation error, eccentricity of the line of sight (collimation axis), vertical index error, and other cyclic errors caused by internal optical or electrical interference. The second category contains systematic errors, which cannot be modeled by mathematical functions. Their influence depends on a type of instrument used, on the physical characteristics of the scanned surface and partially on physical characteristics of the environment in which measurements are performed. These errors cause outliers in point cloud (“fake reflection” when edges and close objects are scanned), their number and size depend on specific scanning conditions. The mathematical model of distance correction can be defined by the following formula (Lichti and Skaloud 2010):



∆d = A0 + A1 d + A2 cos ζ n   2π kd   2π kd   + ∑  A2 k +1 sin    .  + A2 k + 2 cos   k =1   U1    U1 

(6.11)

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The first two terms A0 and A1 in the formula (6.11) are the additive constant and the scale error of the EDM. The third A2 model the vertical offset of the laser axis (laser beam) from the trunnion axis (rotation axis of the rotating mirror, Fig. 6.6) (Lichti and Franke 2005). The sum of the goniometric terms represents the cyclic errors caused by internal optical or electrical interference, where U1 is one half of the wavelength of the shortest modulating wave of the measuring signal. The most important are the first- and second-order terms but higher-order terms can be also used. (Salo et al. 2008). In the case of time-of-flight distance measurement, the Eq. (6.11) is simplified to ∆d = A0 + A1 d + A2 cos ζ .



(6.12)

If the abovementioned formulas do not describe the errors of the EDM sufficiently, it is possible to extend them by other empirical terms (coefficients). The mathematical model of correction of horizontal directions can be expressed by (Lichti and Skaloud 2010): ∆α = B1α + B2 sin α + B3 cos α + B4 sin 2α + B5 cos 2α + B6 csc ζ + B7 cot ζ + B8 d −1

(6.13)

n



+ ∑ ( B2 k + 7 cos ( kζ ) + B2 k +8 sin ( kζ ) ) k =1



The first term B1 in the formula defines the scale error of the horizontal encoder (horizontal circle in optical theodolites); the terms B2and B3 model the eccentricity of the horizontal circle (Schneider and Schwalbe 2008). The next terms B4 and B5 model the errors caused by the non-orthogonality of the horizontal circle and the vertical axis of the instrument. The term B6models the collimation error caused by the non-orthogonality of the line of sight (collimation axis) and the horizontal (trunnion) axis. The non-orthogonality of the horizontal axis and the vertical axis is defined byB7. The eccentricity of the collimation axis relative to the vertical axis is expressed with the term B8, while its influence is most significant at short distances. The summation represents the terms of a Fourier series used to model the oscillation of the horizontal axis of the scanner (Harvey and Rügerer 1992), (Lichti 2007). If needed, the equation can be extended by other empirical terms. The correction of zenith angles can be modeled using the following formula:



∆ζ = C0 + C1ζ + C2 cos ζ + C3 cos 2ζ + C4 sin 2ζ + C5 d −1 + C6 sin 3α + C7 cos 3α

(6.14)

The term C0defines the vertical circle index error, andC1 expresses the scale error. The eccentricity of the vertical circle is expressed by the term C2. The coefficients C3and C4define the error caused by the non-orthogonality of the vertical circle and the horizontal axis of the instrument. The eccentricity of the collimation axis relative to the horizontal axis is expressed by C5. The last two coefficients C6and C7

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model the mechanical oscillation of the vertical axis caused by a mass imbalance in the instrument (Kersten et al. 2005), (Lichti 2007). In this case, it is also possible to extend the equation by other empirical coefficients if the equation is not sufficient for modeling the systematic errors of the zenith (or vertical) angle determination. The abovementioned mathematical models are not universal therefore it is not possible to apply them generally for each instrument. Each scanner is a unique product; it means that the instrument errors are a little bit different (some errors have an influence on the results, some of them can be eliminated), and last but not least, they depend on the calibration performed by the manufacturer. The individual terms of error models have to be adapted to the constructional and functional principle of the instrument tested. If necessary, additional terms can be added, which adequately describe the errors in the results of the measurement. These can be identified in the self-calibration process of the instrument used (Lichti and Skaloud 2010).

6.4.2  Calibration of Terrestrial Laser Scanners Two different approaches can be used for the calibration of scanning systems. The first one is the calibration of individual components of the instrument (distance measurement instrument, horizontal circle, vertical circle, etc.). The second approach is the self-calibration of the whole system as one whole (system calibration). The calibration of the scanner’s EDM can be done on a testing baseline for electronic distance meters. By the execution of the series of measurements, it is possible to estimate the additive constant and the scale error of the EDM. Since laser scanners do not have any telescope for targeting at a point in two faces of the telescope, it is impossible to determine the axis errors of the instrument using standard calibration procedures used for surveying instruments (e.g., total stations). Some of the present laser scanners enable to verify and then to correct some of the systematic errors, e.g., vertical circle index error, horizontal axis error (inclination of the horizontal axis), collimation error, and scale error of the EDM, or they enable ­rectification of dual-axis compensator. The abovementioned errors are identified on a base of measurements of reference points (located according to the requirements of the producer), signalized with special targets, in “two faces” of the instrument (two measurements shifted by 200g). The entire test process is managed by the corresponding function of the scanner’s control software. The calibration of the instruments realized by the producers includes the system calibration of the distance measurement instrument and the rotary encoders (horizontal and vertical circles) on a base of measurement of a large number of reference points, whose positions are determined with higher accuracy as by scanning (e.g., using laser trackers). The instruments are mounted in climate test chambers and tested by various temperatures. An integral part of the process is the calibration of the instrument’s compensator. Finally, the built-in camera is calibrated, i.e., the parameters of the lens and image sensor are estimated. The internal camera’s

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Fig. 6.22  Self-calibration of Trimble GS200 Laser scanner (Chow et al. 2010)

calibration parameters are determined based on the difference between the coordinates of reference points determined by scanning and from images (San 2011). Systematic errors can still be present even after accurate laboratory calibration realized by the manufacturer. For a detailed analysis of systematic errors and their influence, self-calibration procedure based on measurement of reference points (reference network of artificial targets or planar surfaces) is used (Bae and Lichti 2007). The calibration procedures suitable for self-calibration of scanning systems are based on the measurement of a large number of redundant data (multiple scanning) from various stations of the instrument with various positions and orientation. The main advantage of self-calibration is that no special tools are necessary, and they can be performed by the users without the need of intervention into the hardware of the scanner (Al-manasir and Lichti 2015). The only requirement is to build a network of reference points or reference objects (cylindrical, spherical surfaces, planes), whose position is scanned from various scanner positions. The most suitable configuration is to place the reference targets in the whole space around the tested scanner (in each quadrant, on the ceiling, and also on the floor) (Fig. 6.22). However, the result of scanning is a point cloud defined by 3D coordinates of points X, Y, and Z; the measured data are the slope distance d, horizontal direction α, and zenith angle ζ (resp. vertical angle) (Chow et  al. 2010). The determining equations of measured values by measuring point i from the station j are defined by the following formulas:

dij = Xij2 + Yij2 + Z ij2 + ∆d



(6.15)

6.4  Accuracy and Calibration of Terrestrial Laser Scanners



 Yij α ij = arctg  X  ij



 X2 +Y 2 ij ij ζ ij = arctg   Z ij 

  + ∆α    + ∆ζ  

111

(6.16)

(6.17)

The self-calibration consists of three main steps. The first one is to create mathematical models of instrument errors. These models should be created for each instrument, as there are no universal mathematical models describing the systematic errors of every instrument regardless of the constructional and functional principle. It means basically the formulation of individual transformation function between determined and determining variables. The second step of the self-calibration is scanning of the reference targets. The third step is the estimation of the terms of equations of error models and correction of results, in fact, the measured values d, α, and ζ by estimated correctionsΔd, Δα, andΔζ and subsequent calculation of coordinates of the points of the cloud (Lerma and García-San-Miguel 2014). Examples of calibration of laser scanners are described in detail in (Al-manasir and Lichti 2015), (Chow et  al. 2013), (Chow et  al. 2010), (Lichti and Franke 2005), (Lichti 2007), (Reshetyuk 2006), and (Molnár et al. 2009).

6.4.3  Laboratory Tests of Laser Scanners The results of TLS data processing (modeled objects, surfaces, sections, etc.) are created from a large number of measured points, except when the resulting model is created by curves, and the edges of the object are modeled from the points lying as close as possible (without any regression). It means that the real accuracy of the modeling results will be higher than the uncertainty in the position of measured discrete points of a cloud. Most of the producers characterize the accuracy of s­ urface modeling (mainly planar surfaces) by dispersion of data, it means by the dispersion of measured points around the modeled surface (noise). The accuracy of the resulting model can be expressed also by verification of geometrical parameters of the modeled object (parallelism of surfaces, distance between structural elements, etc.). To characterize the accuracy of the results of scanning, it is also necessary to investigate the variation of the accuracy of the model created depending on the distance between the scanner and the scanned object, depending on the position of the modeled surface considering the position of the instrument, depending on the field of view of the instrument used and depending on the resolution (density of points) of point cloud (Zámečníková 2007). The issue of determination and verification of characteristic parameters of laser scanners is discussed in several publications worldwide. Most of these papers describe series of tests that are

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Fig. 6.23  Testing the distance accuracy by planar targets (Johansson, 2002): (a) distribution of targets, (b) test target

aimed at testing the accuracy of distance measurement, angle measurement, testing the influence of the reflectivity of the scanned surface, and the angle of incidence of the laser beam on the accuracy of measured distances. Some of them, are aimed at testing the instrument errors or testing the geometry of the scanned object. Testing the distance measurement accuracy is often performed by scanning of targets or various geometric shapes (planar surfaces, various 3D features) with known position and geometry. The distances between the targets (modeled features) obtained by TLS are compared with the distances obtained by another more accurate method. For instance, Johansson (2002) shows the procedure of testing the distance measurement accuracy by scanning of planar targets. Altogether five targets were placed at a distance of 5 m, 25 m, 50 m, and 80 m from the first planar target (Fig. 6.23a), while each target was placed approximately in the height of the horizon of the scanner tested. The position of the targets was determined by a total station. Each target was measured in 5 points, which create 4 vertices and the center of a square on the target (Fig. 6.23b). The resulting position was determined as the average value of these measurements, which minimized the error of the imperfect target orientation. Targets were scanned repeatedly with various scanning resolution. Their position was modeled by regression planar surface. The distances between modeled planar surfaces were determined in all combinations (1–2 to 4–5), subsequently, they were compared with the distances obtained by the total station. For example, for the instrument Cyrax 2500, the difference in distances did not exceed 2 mm in any cases. Most tests proposed for testing the angle measurement accuracy, or the influence of the uncertainties in the determination of the horizontal direction and the zenith

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113

angle on the results of measurement, are based on the scanning of a reference point network. In most cases the points are signalized by spherical targets or special targets, which can be identified automatically by the instruments. Their position has to be determined by method ensuring higher accuracy as the accuracy of the scanning itself. The structure of the reference network must enable the deriving and analysis of uncertainties in the measurement of the horizontal direction and the zenith angle from the distance differences between the scanned targets. An approach for testing the influence of uncertainties in angle measurement was proposed by (Boehler et al. 2003). The method used expects that the errors in the angle measurement could be identified by comparison of a short distance obtained from scanning with its reference value (obtained by another method with higher accuracy). The distances are determined between a pair of spherical targets, which are at the same distance from the instrument (to minimize the effect of uncertainties in the distance measurement). Tests investigating the reflectance of the surface of the object scanned and the angle of incidence between the laser beam and the surface are aimed at analyzing the accuracy of distance measurement depending on the surface characteristics as well as the angle of incidence. In most cases, the tests are performed by scanning planar surfaces with various orientation, while the targets differ in material, color (matte and shiny also), as well as in texture. The impact of different shapes, materials, and colors of the scanned surface on the accuracy on the results is investigated in (Clark and Robson 2004), (Křemen 2004), (Koska et al. 2004), and (Křemen 2005). Testing the geometry of scanned objects often based on scanning the edges and subsequent analyses of the quality of their identification in scan results or on testing of spatial models as the results of scanning and processing. For instance, Boehler et al. (2003) deal with testing the quality of scanning edges and the possibility of multiple reflections in the point cloud. The edges of scanned objects were simulated using two panels placed in the close proximity of each other (Fig. 6.24a). They categorized the quality of the identification of edges as low, average, and high (Fig. 6.24b). Complex technological procedure for testing laser scanners, based on the knowledge of characteristics of the objects of real scene scanned is described in Zámečníková

Fig. 6.24  Testing the quality of edges scanning (Boehler et al., 2003): (a) test panels, (b) representation of quality from high (up) to low (down)

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Fig. 6.25  3D test bodies for complex testing

(2007). Real objects are represented by two reference bodies of c­ ylindrical and rectangular shapes (Fig. 6.25). The first test body is created by two cylinders with the radius of the bases of the cylinders of 400 mm and 180 mm, respectively. The second test body is created by two rectangular blocks with parameters of 450 mm × 450 mm × 250 mm and 150 mm × 150 mm × 250 mm. The cylinders are placed on each other with a common rotation axis. The height of both cylinders is 250 mm. The surface of both test bodies is colored with a matte gray color. Their geometric parameters were determined by photogrammetry. During testing, they were located in various spatial positions at various distances from the instrument tested and were scanned with various parts of the field of view of the instrument. To investigate the mutual interaction of the instrument and the scanned scene, four types of test measurements were used. The first type is the POSITION. The aim of this type of test is to verify the influence of changing spatial position of the reference body on the geometry of the model obtained. The spatial position of the reference figures changes with their rotation in the horizontal and vertical direction. The second type is DISTANCE.  The aim of this is to determine the influence of the changing distance of the reference body from the scanner on the quality of the model obtained. The third type is HOMOGENITY. The aim is to verify the parameters of the instrument if they are stable during the whole measurement. The reference bodies are placed in various parts of the field of view of the instrument. The fourth proposed type of tests is MODELED POINTS, by which the 3D position of the modeled points of the reference body is verified (Zámečníková 2007). Testing of scan accuracy using reference bodies is described in (Erdélyi and Kubík 2010). The geometric parameters of the models of reference solids obtained by scanning and by measurement using a coordinate measuring machine (CMM) are compared. The quality analysis of the resulting 3D models was realized by comparison of the lengths of edges and the standard deviations of regression models

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(plane, cylinder) created from the data of both methods. For instance, in the case of instrument Leica ScanStation2, the average of absolute values of the differences in lengths of edges obtained by TLS and CMM was 0.7 mm.

6.4.4  Field Tests of Terrestrial Laser Scanners The procedures described in the previous chapter are simpler than the calibration procedures but are still quite time-consuming. Execution of the tests from preparation, through scanning, to the analysis of results, often requires several days. Therefore, most of them are not suitable for “quick” and easy check of the instrument used (e.g., in the field before the measurement). A series of standards, ISO 17123 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments – Parts 1–9, deals with testing of instruments in the field. This series describes the procedure for verification of parameters of instruments tested in field conditions. The standards contain standardized procedures for measurement and processing of results, which allow the users to obtain information about the current state of the instrument in a simple way. The last part of the series deals with terrestrial laser scanners, ISO 17123-9 Optics and optical instruments – Field procedures for testing geodetic and surveying instruments  – Part 9: Terrestrial laser scanners. The testing procedure suggested in the mentioned standard is described in the next part of this chapter. The standard defines a simplified and full test procedure of terrestrial laser scanners. The simplified procedure is based on the limited number of scanning of artificial targets without a known reference position and subsequent analysis of the distances between them. The standard prescribes the distribution of four targets so that their configuration creates one horizontal and one vertical triangle (Fig. 6.26). Both triangles have to have one edge common whereby the distribution of targets in their vertices has to respect the recommendations of manufacturers of instrument tested (maximal distance from the instrument, orientation). For instance, for Leica ScanStation2, the manufacturer prescribes a maximal recommended distance of scanning the targets of 100 m. The targets are scanned from two stations of the instrument, which are situated in the following configuration: stations S1 and S2 and two targets T1 and T2 lay on one line (Fig. 6.26). Such configuration of stations enables to identify the systematic error in distance measurement. Triangles should be right-angled while the hypotenuse of the horizontal triangle should not exceed the maximal recommended distance of target scanning (m.d.) given by the producer. The height of the vertical triangle defined by the distance between targets T2 and T4 should be approximately 1/2 of m.d. (at least 1/3 m.d.), while the target T4 should be scanned from station S1 under a vertical angle of minimal 27° (maximal zenith angle of 63°). During scanning of targets, the instrument has to be “oriented” to the center of the line between T2 and T3 while the

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Fig. 6.26  Testing laser scanners on the base of ISO standard: (a) horizontal triangle, (b) vertical tringle

orientation between the stations of the scanner should be rotated by 200g. Such orientation of the instrument is important especially in the case of panoramic scanners using a rotating mirror as the projection mechanism. These scanners scan the whole scene by turning only 200g around the vertical axis. This orientation ensures that target T3 and T2 are scanned quasi in two faces. In the case of instruments, which enable automated measurement of targets in two faces, only data from the

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second face measurement of the target T3, and only data from the first face measurement of the targets T2 and T4 are taken into the account when processing the data. Conversely, when processing the data from the station S2, only data from the first face measurement of the target T3 and only data from second face measurement of the targets T2 and T4 are considered. Before the measurement, the instrument must be acclimated (it is recommended to wait for 2 min per 1 °C of temperature difference). During the test, it is necessary to note the atmospheric conditions (pressure, humidity, air temperature). If the instrument allows, the atmospheric conditions are entered directly into the control software of the scanner (then the correction are calculated automatically). Otherwise, the atmospheric corrections have to be calculated manually and applied to the measured quantities. The standard also recommends that the conditions chosen for tests should correspond with those expected during the scanning. The results of measurement are coordinates X, Y, and Z of the targets T1 to T4 from two stations of the scanner. In the case when the instrument used does not allow automated identification of targets, it is necessary to model them manually while the use of the software suggested by the producer is recommended. Length between targets in all possible combinations 1–2 to 3–4 from both stations is calculated from the coordinates of points, which represents a total of 12 lengths. Subsequently, the differences of identical lengths Δ12 to Δ34 are calculated from all stations, in total six differences. When analyzing the distance measurement, horizontal and vertical angle measurement, the absolute values of the length differences are compared with the expanded uncertainty of their determination UΔ, which can be calculated from the standard deviation of the determination of the target’s center UT. Its value can be given by a priori characteristics of the instrument. The manufacturer either defines its value directly or it can be calculated from the a priori characteristics of the instrument used by the application of the uncertainty propagation law. Another possibility is to determine the uncertainty of the determination of the target’s center from the data obtained by repeated scanning of the targets. Applying the uncertainty propagation law, it is possible to calculate the uncertainty of the determination of length between the targets using the following formula:

uSC = uT 2.

(6.18)

The formula for calculation of uncertainty of length differences can be written as follows:

u∆ = uSC 2.

(6.19)

The expanded uncertainty of the determination of length differences can be calculated by multiplication of the uncertainty of the length differences by the coefficient of expansion according to the following formula:

U ∆ = k u∆ .

(6.20)

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Assuming that the measured values belong to a normal distribution and for confidence interval of 95%, the coefficient of expansion is k = 2. The accuracy analysis of the distance measurement assumes that the distance between targets T1 and T2, determined from station S1, is not influenced by any constant error (similar to the additive constant EDM). On the other hand, by its determination from the station S2, this error is doubled. The analysis is based on the comparison of the absolute value of the length difference with its extended uncertainty. If |Δ12| > UΔ, it means that the distance measurement is influenced by a systematic error. In that case, it is necessary to set the value of distance correction into the instrument (a half from Δ12 if the instrument allows it), or it is necessary to calibrate the instrument. To investigate the quality of the angle measurement the remaining length differences are compared with their extended uncertainty. If |Δ13| > UΔor |Δ14| > UΔor |Δ23| > UΔor |Δ24| > UΔ or|Δ34| > UΔ, it is recommended to realize the complex procedure of testing described in the standard, alternatively it is necessary to calibrate the instrument. The measurement workflow for the full test procedure is similar to the simplified. A series of measurement is performed from each station of the instrument, while the position of the scanner has to be shifted by a few centimeters between the measurements. The full test procedure is quite difficult, because when calculating the extended uncertainty of the length difference determination, it is necessary to identify and mathematically model the sources of errors affecting the scan accuracy.

References Al-manasir, K., & Lichti, D.  D. (2015). Self-calibration of a Lecia HDS7000 scanner. In FIG Working Week 2015 (Ed.), Technical programme and proceedings. Sofia, Bulgaria, 17.  – 21.5.2015 (p. 12). Copenhagen: International Federation of Surveyors. Amberg Technologies. (2018). Amberg clearance IMS 5000. https://ambergtechnologies.com/fileadmin/user_upload/amberg-technologies/downloads/Rail/Clearance_IMS5000_Datasheet_ en.pdf. Accessed 16 Dec 2019. Bae, K., & Lichti, D. D. (2007). On-site self calibration using planar features for terrestrial laser scanners. In Proceeding of the ISPRS workshop on laser scanning 2007 and SilviLaser 2007, Espoo, 12–14 September 2007. Baltavias, E. P. (1999). Airborne laser scanning: Basic relations and formulas. ISPRS Journal of Photogrammetry and Remote Sensing, 54(2–3), 199–214. Baník, I., et al. (2007). Fyzika a elektronika 1. Východisko modernej techniky (Physics and electronics 1. The basis of modern technology). Bratislava: Vydavateľstvo STU. Beraldin, J. A., et al. (2010). Laser scanning technology. In G. Vosselman & H. G. Maas (Eds.), Airborne and terrestrial laser scanning (pp. 1–42). Dunbeath: Whittles Publishing. Besl, P. J., & McKay, N. D. (1992). A method for registration of 3-D shapes. IEEE Transactions on Pattern Analysis and Machine Intelligence, 14(2), 239–256. Boehler, M., Bordas, A., & Marbs, A. (2003). Investigating laser scanner accuracy. http://i3mainz. de/sites/default/files/public/data/laserscanner_accuracy.pdf. Accessed 22 July 2018. Boor, C. (1978). A practical guide to splines. New York: Springer. Chow, J. C. K., et al. (2010). Self-calibration of the Trimble GS200 terrestrial laser scanner. In International archives of photogrammetry, remote sensing and spatial information sciences (Vol. 38, p. 6). Calgary: ISPRS.

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Chow, J. C. K., et al. (2013). Improvements to and comparison of static terrestrial LiDAR self-­ calibration methods. Sensors, 13(6), 7224–7249. Clark, J., & Robson, S. (2004). Accuracy of measurements made with a Cyrax 2500 laser scanner against surfaces of known colour. In Proceedings of the XXth ISPRS congress, Istanbul, 12–13 July 2004. Ding, Q., & Davies, B. J. (1987). Surface engineering geometry for computer-aided design and manufacture. New York: Ellis Horwood. Erdélyi, J., & Kubík, M. (2010). Analýza kvality 3D modelov vytvorených z údajov získaných terestrickými laserovými skenermi (quality analysis of 3D models created from data obtained by terrestrial laser scanners.). In Geodézia, kartografia a geografické informačné systémy 2010. Košice: FBERG TUKE, 7–9 September 2010. Ge, X. (2016). Terrestrial laser scanning technology from calibration to registration with respect to deformation monitoring. Dissertation, Technical University of Munich. Grilli, E., et al. (2017). A review of point clouds segmentation and classification algorithms. In International archives of the photogrammetry, remote sensing and spatial information sciences (Vol. 42, p. 5). ISPRS. Harvey, B.  R., & Rügerer, J.  M. (1992). Theodolite observations and least squares. Australian Surveyor, 37(2), 120–128. Johansson, M. (2002). Explorations into the behaviour of three different high-resolution ground-­ based laser scanners in the built environment. In International archives of the photogrammetry, remote sensing and spatial information sciences (Vol. 25, p. 6). ISPRS. Kersten, T. P., et al. (2005). Investigation into the accuracy behavior of the terrestrial laser scanning system Mensi GS100. In: Proceedings of optical 3-D measurement techniques VII, TU Vienna, 3–5 October 2005. Koska, B., et al. (2004). Development of rotation scanner, testing of laser scanners. In: Proceedings of the 3rd international conference on engineering surveying – INGEO 2004, Slovak University of Technology, Bratislava, 11–13 November 2004. Křemen, T. (2004). Testování laserového skenovacího systému Cyrax 2500 (Testing of the Cyrax 2500 laser scanning system). In Juniorstav 2004. Brno: VUT, 4–5 February 2004. Křemen, T. (2005). Testování terestrických laserových skenovacích systémů (testing of terrestrial laser scanner systems). In Juniorstav 2005. Brno: VUT, 2 February 2005. Leica Geosystems. (2019). Leica Pegasus: Two mobile sensor platform. https://leica-geosystems. com/kk-kz/products/mobile-sensor-platforms/capture-platforms/leica-pegasus_two. Accessed 16 Dec 2019. Lerma, J.  L., & García-San-Miguel, D. (2014). Self-calibration of terrestrial laser scanners: Selection of the best geometric additional parameters. In ISPRS annals of the photogrammetry, remote sensing and spatial information sciences (Vol. 2, p. 8). ISPRS. Lichti, D. D. (2007). Modelling, calibration and analysis of an AM-CW terrestrial laser scanner. ISPRS Journal of Photogrammetry and Remote Sensing, 61(5), 307–324. Lichti, D. D., & Franke, J. (2005). Self-calibration of the iQsun 880 laser scanner. In: Proceedings of optical 3-D measurement techniques VII, TU Vienna, 3–5 October 2005. Lichti, D. D., & Skaloud, J. (2010). Registration and calibration. In G. Vosselman & H. G. Maas (Eds.), Airborne and terrestrial laser scanning (pp. 83–133). Dunbeath: Whittles Publishing. Luhmann, T. (2006). Close range photogrammetry. Dunbeath: Whittles Publishing. Mäntylä, M. (1987). An introduction to solid modelling. New York: Computer Science Press. Molnár, G., et al. (2009). On-the-job range calibration of terrestrial laser scanners with piecewise linear functions. Photogrammetrie – Fernerkundung – Geoinformation, 2009(1), 9–21. Nguyen, A., & Le, B. (2013). 3D point cloud segmentation: A survey. In: 6th IEEE conference on Robotics, Automation and Mechatronics (RAM), IEEE, Singapore, 12–15 November 2013. Piegl, L., & Tiller, W. (1995). The NURBS book. Berlin: Springer. Rabbani, T., et al. (2007). An integrated approach for modelling and global registration of point clouds. ISPRS Journal of Photogrammetry and Remote Sensing, 61(6), 355–370.

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Reshetyuk, Y. (2006). Investigation and calibration of pulsed time-of-flight terrestrial laser scanners. Dissertation, KTH Royal Institute of Technology. Salo, P., Jokinen, O., & Kukko, A. (2008). On the calibration of the distance measuring component of a terrestrial laser scanner. In International archives of the photogrammetry, remote sensing and spatial information sciences (Vol. 37, p. 5). ISPRS. San, R. (2011). Leica ScanStation calibration and QA. https://cms.leica-geosystems.us/wp/psg/ files/2013/downloads/Leica%20ScanStation%20Calibration%20and%20QA.pdf. Accessed 22 Jul 2018. Schneider, D., & Schwalbe, E. (2008). Integrated processing of terrestrial laser scanner data and fisheye-camera image data. In International archives of the photogrammetry, remote sensing and spatial information sciences (Vol. 37, p. 7). ISPRS. Smith, M. W. (2015). Direct acquisition of elevation data: Terrestrial laser scanning. In S. J. Cook et al. (Eds.), Geomorphological techniques. London: British Society for Geomorphology. Štroner, M., et al. (2013). 3D skenovací systémy (3D scanning systems). Praha: ČVUT. Vosselman, G., & Klein, R. (2010). Visualisation and structuring of point clouds. In G. Vosselman & H. G. Maas (Eds.), Airborne and terrestrial laser scanning (pp. 45–81). Dunbeath: Whittles Publishing. Wehr, A., & Lohr, U. (1999). Airborne laser scanning  – An introduction and overview. ISPRS Journal of Photogrammetry and Remote Sensing, 54(2–3), 68–82. Wujanz, D. (2016). Terrestrial laser scanning for geodetic deformation monitoring. Dissertation, Technical University of Munich. Xu, Y., et al. (2018). Voxel-based segmentation of 3D point clouds from construction sites using a probabilistic connectivity model. Pattern Recognition Letters, 102, 67–74. Zámečníková, M. (2007). Testovanie terestrických laserových systémov (Testing of terrestrial laser systems). Dissertation, Slovak University of Technology, Bratislava.

Chapter 7

Coordinate Measuring Systems and Machines

A development of production processes mainly in mechanical engineering production (a car industry, aviation, space industry) but also in the other similar industries causes increasingly requirements on the accuracy of a realization of products. Coordinate measuring machines are very important tools for quality checks in all kinds of manufacturing, mainly when automated processes are implemented. The knowledge of their principles, specifications, and basic rules of possible use is very important for the surveyors as well as the equality managers. The chapter brings the categorization and functional principles of coordinate measuring machines and procedures for their testing and calibration and discusses the accuracy of measurement results.

7.1  Principle of Coordinate Measuring Machines A verification of geometrical parameters of products (components) as well as a verification of geometrical parameters of production machines and systems by methods of reverse engineering and industrial metrology is a necessary part of an assurance of the continuous production process. Coordinate measuring machines (CMMs) and systems are very important tools for quality checks in all kinds of manufacturing, mainly when automated processes are implemented. Coordinate measuring systems (CMSs) enable to determine spatial coordinates of reference points, eventually points located on a surface of a measured object with accuracy in micrometers (in general with nominal accuracy better than 1:10,000). CMS consists of a CMM and of a control computer with an operating software for measurement and evaluation of results. The disadvantage of CMMs, in comparison to the traditional geodetic technologies, is their limited measuring range (maximum several tens of meters by particular selected CMMs). Methods and determination of coordinates are based on known geodetic methods, the polar method, or distance measurement in three directions which are perpendicular to each other. According © Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_7

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to that, the area of industrial metrology, which apply CMMs as a tool to ensure the metrological trecebility, is related to the industrial surveying. Measurements are realized in the same conditions; the only difference is the rapidly larger maximal dimension of a measured object by geodetic methods. On the other hand, the accuracy of CMM is much higher. CMSs are generally produced in small series, or made-to-measure according to the requirements of certain service (client). Individual components of the system are produced in series for the majority of systems, but the result is the specific system that generally serves for the repeated specific measurements. The functional principle of CMMs, their categorization according to various criteria, and the characteristics of the error sources by determining the coordinates with the help of CMM are described in the following chapters.

7.2  Categorization of CMMs The development of coordinate measuring technique stimulates also the formation of new terminology. According to the complexity of the measuring configuration, CMMs can be categorized into (Brezina 1987): • Coordinate measuring instrument (CMI) – a measuring tool which creates a system of orthogonal, polar, or cylindrical coordinates with a contact or contactless scanning of coordinates • Coordinate measuring machine (CMM) – a machine with the typical construction which represents mechanical connection of two (three) perpendicular located lines, in general, by mechanization or automation of a certain function (i.e., movements) with a contact or contactless scanning of coordinates • Automated coordinate measuring machine – the CMM equipped with a control and processing system (computer, a microprocessor), which enables to realize an automated measuring cycle for measurement of coordinates and parameters of the measured object • Coordinate measuring robot – the CMM equipped with several robotic features (manipulating and transporting equipment, signalizing of overcoming the given limits, etc.). The majority of authors who deal with the problem of measurement of geometrical parameters in mechanical engineering involve the area of coordinate measuring instruments’ wider range of instruments and equipment, i.e., measuring microscopes and projectors: • Measuring microscope – it is the CMI which enables measurement of coordinates and parameters generally in a plane, in contactless mode (using optical sensors). They are equipped with a measuring base with two perpendicular shifts to each other (in XY direction) and then with a reading device; the latest models are possible to connect with a computer, so measured coordinates are directly

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recorded onto a storage medium, or the whole measurement could be managed by the computer. The incremental sensors with the resolution up to 0.01 μm are used to determine the coordinates. The measuring range of microscopes is limited to 400 mm in the direction of the X axis and Y axis. • Coordinate measuring projectors – they are the CMIs with the projector equipment, which enables to measure coordinates of chosen characteristic points of the measured object on a magnified picture in a plane. The magnified picture of the part of an object is projected on the ground-glass plate where it is compared with the transparent drawing; eventually, coordinates are measured by micrometric screws of a measuring base (table). The measuring range and resolution depend on magnification of the used optical equipment, and it is similar to the measuring range and resolution of the measuring microscopes. The connection of the coordinate measuring projector and personal computer enables the automation of the measuring process. The CMMs are divided according to the method of determination of coordinates of the measured point into: • Polar – measuring arms, which have stabile length of an arm and in-built angle sensors in joints of the measuring arm. Laser trackers also belong to the category of polar CMM.  Laser trackers are measuring systems similar to total stations whereby the distances are measured by interferometric method. Because of this interferometric distance measurement, it is possible to determine the coordinates of the measured point with the higher accuracy (0.01 mm) in comparison to total stations. • Orthogonal – the CMM created by a fixed frame, which enables a motion of sensor head (in contact mode or contactless mode) in perpendicular directions to each other (from 1D up to 3D). The development of the CMMs starts mainly from experience in the construction and production of the coordinate machine tools. The shape and construction of the CMMs have been developed continuously according to the customer requirements from various industries, and therefore it is adapted to the specific requirements (Fig. 7.1). According to the form and configuration of stable and moving elements of the CMM, it is possible to divide the orthogonal measuring machines according to (Brezina 1987) and (Kopáčik 1998) into: • Cantilever/console CMMs – they are mainly used by measurements with high accuracy. These are mainly the CMMs with a limited range of measurement (they are relatively small) and generally are installed in laboratories or in those parts of operating halls that are reserved for quality control of production. A lot of them are equipped with a sensor system for measurement of polar or cylindrical coordinates. • Horizontal arm CMMs – they are characterized by nonlinear configuration or by several times higher range in the direction of the X axis than in the other axes. Their measuring range can be relatively big, and they are generally installed in

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Fig. 7.1  Categorization of orthogonal/Cartesian CMM according to the configuration of their stable and moving elements (Hexagon 2016): (a) cantilever/console CMM, (b) horizontal arm CMM, c gantry CMM, (d) bridge CMM

operating parts, mainly in the car industry. There are also CMMs produced with two arms opposite each other called the double arm CMM. • Gantry CMMs – they are characterized by a high consistency of the construction. The gantry CMMs can be divided into the CMMs with a moving or stable portal. The CMMs with the stable portal have a moving measuring base. In practice, the CMMs with the moving portal are used more because thanks to their stable measuring base they offer a big fastening area with high consistency. The range of the portal CMMs is generally up to several meters. They can be installed in laboratories for the precise reverse engineering or directly in operating conditions in various kinds of industries.

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125

• Bridge CMMs  – they were developed for the measurement of big structures. They have a big measuring range up to several tens of meters. Keeping the required accuracy of measurement and high consistency of a machine construction is very important; it can be achieved by the massive (robust) designed beams and columns. The bridge CMMs are mainly installed in the operation of the car industry and aviation.

7.3  Polar CMMs The development of the polar CMMs is the fastest developing part of the CMM production. The polar CMMs enable the precise determination of coordinates on a base of measured polar coordinates (an angle, a distance). Polar CMMS are transportable coordinate measuring systems, which enable inspection of geometric parameters of the measured object directly during its operation. They are used for verification of objects the transport of which to the operation space of the orthogonal CMMs, would be difficult because impossibility of removal of the verified component or for verification of geometrical parameters of parts of big industrial of objects in operation. Because of their easy manipulation by movement, they are used in all industries, from the verification of machines through a car industry up to aviation. The polar CMMs are divided into two main categories according to the functional principle and construction: • Measuring arms • Laser trackers Measuring arms are the CMMs consisting of several arms with a stable length which are connected to each other by joint mechanisms and which enable independent rotation of each arm. Length of arms is fixed (it is not measured because it is given by a producer), and only an angle of rotation of each arm to each other is measured by angle sensors in-built in joints of measuring arm (Fig. 7.2). Currently measuring arms are produced with various lengths from 1 m up to 4.5 m. It should be taken into account that the arm of higher longitude is able to ensure lower accuracy. Measuring arms enable the utilization of various types of sensor systems. Using the contact probing system, it is possible to determine coordinates of chosen points selectively according to operator option with accuracy up to 0.02 mm. The contactless probing systems are increasingly used in reverse engineering. Using the measuring arm together with the laser scanning head enables us to scan the whole surface of the measured object with an accuracy of 0.05  mm. In both cases, the results enable the verification of geometrical parameters as well as the creation of an accurate replica (3D model) of the measured object. Laser trackers are the CMMs measuring on a principle of total stations. These are measuring systems developed for a precise measurement of coordinates of

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Fig. 7.2  Measuring arm (left) and angle sensors in-built in the joint mechanism of CMM (right) (Hexagon 2015b)

reference points of big objects. The determination of directions (angles) is ensured by the same sensors as it is by current available total stations of the highest accuracy level (accuracy of angle measurement is up to 0.15 mgon). The difference from total stations is in the distance measurement, which is realized by an interferometric measurement. The measuring range of the current laser trackers is up to 160 m with the help of special reflecting prisms. Uncertainty of the determination of the position  of a measured point caused by the uncertainty of the angle measurement is 10  μm  +  2.5  μm/m and uncertainty caused by the distance measurement is 2 μm + 0.4 μm/m. The majority of laser trackers enable to use contact as well as contactless probing systems. The contact probing systems enable to determine coordinates of selected reference points of a measured object without any usage of specialized equipment for the installation of reflecting prisms (Fig. 7.3). An operator chooses measured points by touching of the stylus of the probing system, whereby a laser tracker determines their position on a base of measured coordinates of targets situated on the probing system (similar to a measurement of an inaccessible point in geodesy). The accuracy of the determination of a point position using a laser tracker in combination with the contact probing system is around several hundredths of a millimeter. Besides the contact probing systems, it is possible to use also contactless scanning heads (Fig. 7.4). Scanning velocity of such systems is several hundred thousand points per second, whereby accuracy of measurement, defined by producers as accuracy of a determination of a scanned plane, is better than 0.1 mm.

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Fig. 7.3  Leica Absolute Tracker AT 960 (left) with contact probing systems B-Probe and T-Probe (right) (Hexagon 2015a)

Fig. 7.4  Scanning of the car mask using the scanning head (Hexagon 2015a)

The current trend of the utilization of laser trackers is their installation directly in production. Probing systems (contact or contactless) are installed on arms of industrial robots, which always repeat the same action in a certain period (they describe the same trajectory) (Fig. 7.4). The position of the probing system is determined with help of laser trackers; this enables the determination of geometrical parameters of produced components at a high accuracy level, whereby the measuring system is part of a manufacturing line. The measuring speed of the currently offered laser

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trackers (several thousand measurements per second) enables also their utilization by dynamic measurements. An important part of the measuring system by the polar CMMs is always the controlling computer with the specialized software for management of measuring process as well as for valuation of measurements (creation of surface models, difference models, identification and quantification of deviations, etc.).

7.4  Orthogonal CMMs Orthogonal coordinate measuring machines have been developed in the last decades. Nowadays they are an important part of the inspection of geometrical parameters of components mainly in mechanical engineering. These are the stable CMM, which are mainly installed in laboratories, specialized on very precise measurements of geometrical parameters of objects or in those parts of operating halls reserved for the quality control of the whole productions. There are also CMMs developed for a specific kind of measurement by a combination of various constructional solutions (see Sect. 7.1). These CMMs realize their measurements repeatedly and are installed directly in production (in operation) mainly in a car industry and aviation, where they enable the automated verification of produced components. From the constructional point of view, each orthogonal coordinate measuring machine consists of parts referred to as (Kopáčik 1998): • • • • • •

Mechanical features (elements) Moving features Measuring devices (sensors) Probing systems Gearings/power drives Operation/control systems (AC)

To the mechanical features of the CMMs consist of a base, measuring table (plate), gantry, bridge, ram, and balancing equipment (Fig. 7.5). Base, according to the CMM type, is represented by a frame or tripod of the CMM. It holds all other stable and moving parts of the CMM. It has to have high consistency to ensure the dimensional stability of the measuring machine also by dynamic stress during measurement. The frame of the coordinate measuring machine is mainly equipped with anti-vibration equipment for the elimination of a surrounding influence and with setting legs, which enable the leveling of the CMM (similar to leveling screws of geodetic instruments). Measuring plate (table) creates a base to which measured objects are connected during measurement. The construction of the table has to ensure dimensional stability, high consistency, as well as high stability (it should not bend down even under the big pressure of heavy load). The measuring plate is mainly created by natural stone (granite).

7.4  Orthogonal CMMs

129

Fig. 7.5 Structure elements of CMM (Hexagon 2016): (a) base, (b) measuring table, (c) portal/gantry, (d) ram

Portal or bridge is moving along the base of the CMM to ensure measurement of coordinates in X and Y directions. These are parts of the CMM, which carry the probing system. The construction of the portal and the bridge has to ensure the consistency and the dimensional stability of the measuring system. Ram is an extension part (arm) of the CMM with a circular or quadrilateral cross-­ section. Ram could be located in a vertical or horizontal position. It is produced from metal and in some cases also from natural stone or carbon fiber. Moving features of the coordinate measuring machines are located in bearings led by linear guide surfaces. High bearing quality of moving groups could be achieved by lapping (high-quality polishing) of natural stone and using aerostatic location. In that case, the moving features are located on an air cushion with thickness of several micrometers which levels the irregularity of the guide surfaces. Roller bearings are used by metal-moving features. The easiest solution is the usage of precise pulleys, but the most used are spherical roller bearings which eliminate the influence of guide surface irregularities, and at the same time their loading capacity enables for the CMM to carry heavy loads. By the CMMs of lower measuring range, it is possible to use a friction bearing of moving features in metal guide

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Fig. 7.6  Measuring systems of CMM: (a) a gear rack with a pinion, (b) a worm shaft, (c) an incremental distance sensor, (d) a linear magnetogenerator

surfaces. The disadvantage of the friction bearing is the lower movement velocity of the CMM (because of high friction) and the fact that the guide surfaces need more maintenance (regular greasing) (Brezina 1987), (Kopáčik 1998). The measuring device of the CMM (Fig. 7.6) consists of a distance or angular measure and reading device, which indicates the length (or coordinate) in an analog or digital mode. As a distance measuring system in the coordinate measuring machines is used: • • • • •

A gear rack with a pinion A worm shaft A linear magnetogenerator An incremental distance sensor A laser interferometer

A gear rack with a pinion and a worm shaft are robust measuring systems resistant to rough treatment. A measured distance is determined indirectly by both of these systems. A particular angular rotation of a pinion or worm shaft is measured, in most cases, at a fraction of the whole rotation. The distance (a measured coordinate) is calculated from the angular rotation and from the whole number of rotations of pinion or worm shaft. Accuracy of measured coordinates depends on a dimension of gearing and accuracy of measured angular rotation; accuracy of current CMMs is 0.01 mm. An incremental distance sensor and a linear magnetogenerator are measuring devices operating under a similar principle. The base of both devices is created by linear scales, which are presented by installed stripes in the direction of active axes of CMM. In the first case, segments (increments) are applied on strips; in the second case, a meander conductor is applied on a strip. A measuring head of the probing system determines the measured distance according to the number of increments

7.4  Orthogonal CMMs

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(segments) measured by optical method or according to the number of increments measured on the base of the induced voltage. Accuracy of the measured coordinate is several micrometers in both cases. An interferometer is the most precise measuring sensor used in the coordinate measuring machines. The CMMs which use the interferometric determination of coordinates have accuracy of 0.01 mm. Because of the high price and the fact that all measurements have to be realized in laboratories, the CMMs using interferometers are the least spread. Angular measuring systems are part of calibration stands which often create accessories to the coordinate measuring machines. They are mainly realized with circular incremental sensors or circular magnetogenerators with a resolution up to 0.15 mgon. An axial gearing is less used (Brezina 1987). A part of the coordinate measuring machines which serves for a determination of a relative point position toward measuring machine is called a probing system. Probing systems can be divided into two main categories (Kopáčik 1998): • Contact systems • Contactless systems Probing systems used in CMMs are described in detail in Sect. 7.5. Drives of the coordinate measuring machines are realized by electromotors, or the drive of the CMMs can be in some cases manual, mainly in measuring microscopes and coordinate measuring projectors. The majority of the CMMs are constructed with a motor drive on direct current connected with a tachometer generator and power element with the regulator, which enables the creation of complex positioning servo controls (Warnecke et  al. 1984). In some cases, the CMM drive is realized by a stepping motor. Drives are limited in the direction of each CMM axis with safety terminal switches. By operating drives, it is possible to define the speed (a range is from 1 μm/s up to 1 m/s) or to define the stepping manually with an operator from the control panel of the CMM, and in the case of automated measurement, the CMM’s drive is operated with the help of the controlling computer (Kopáčik 1998). The control system of the CMMs is a complex of digital-analog electric circuits, which control all movements of the probing system with the help of drives. Commands can be defined manually by the control panel of the CMM or by the controlling computer. According to the level of controlling and connection of a computer, it is possible to distinguish four levels of automation of a measuring process (Warnecke et al. 1984): • • • •

Manual navigation of the probing head Manual navigation from the control panel Computer navigation according to the predefined method Navigation from the parent computer (in a case that the CMM is a part of a manufacturing line)

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Control systems of the coordinate measuring machines can operate in a closedor open-loop string. Systems with the closed-loop string enable us to generate general shaped trajectories of movement of the probing head with optional velocities. Systems with the open-loop string enable us to realize calculations already during measurement. The development of the coordinate measuring machines or robots was first of all stimulated by the necessity of a continual measurement of workpieces in integrated operating parts and automated operating systems. Because of these facts, the current coordinate measuring machines are equipped with a relatively big operating speed and with a possibility of elementary programming. The software of the controlling computer (control software and software for processing) is an integral part of the coordinate measuring machines, which is provided by producers. The level of this equipment, their content, and flexibility are important factors for reviewing the application possibilities of the CMMs. Software provided by producers covers all typical measuring tasks and also the majority of the specific measuring tasks in mechanical engineering (Kopáčik 1998). Modern CNC (computer numerical control) machines can also be included in the category of the orthogonal CMMs (Fig. 7.7). These machines are developed for the precise computer-controlled cutting of components, and nowadays they are an integral part of the industry. A construction of CNC is similar to a construction of the CMMs; by using probing systems instead of cutting tools, it is possible to measure similar to the coordinate measuring system with an accuracy of 0.01 mm.

Fig. 7.7 Portal CNC machine

7.5  Probing Systems of CMMs

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7.5  Probing Systems of CMMs The main task of the CMM is to determine a point position on an object. The part (or an element) of the CMM which serves for a determination of a relative point position toward the measured machine is called a probing system. Probing systems can be divided into two main categories (Brezina 1987), (Kopáčik 1998): • Contact systems, • Contactless systems. Probing systems of the CMM consist of the head of the probing system and the coordinate sensor (a probing). The head of the probing system serves for an attachment of measuring sensors (contact or contactless). Their task is to ensure a sensor rotation into the particular direction around two axes which are perpendicular to each other (horizontal and vertical). Using the head of the probing system enables measurement of coordinates of whatever point of a measured component only with help of a movement of the CMM moving parts and with help of head rotation (360° around the vertical axis and 230° around horizontal axis) (Fig. 7.8). Using stable heads it is possible to measure coordinates only in three perpendicular directions (XYZ), whereby it is necessary to rotate each component or to change its location on the CMM working desk for measurement of coordinates of reference points of the measured component. Contact probing systems are created by a switching probing. The easiest contact probing systems are created by elements switched into a ram of the coordinate measuring machine. The elements in the shape of a cone, sphere, cylinder, etc. are used. Uncertainties in the determination of point position arise as a consequence of various compressive forces during measurement. The CMM producers prefer so-called electro-contact or electric contact probing systems (switching probing). Accuracy

Fig. 7.8  Head of the probing system with a contact probing (Renishaw 2010)

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Fig. 7.9  Stylus with changing system (Renishaw 2013)

of probing systems is characterized by a value of repetition in a contact setting, which ranges from 0.1 μm to 2.0 μm (Brezina 1987). Switching probing consists of a switch and a stylus (Fig. 7.9). After touching the stylus, the switch device generates a signal, which stops a movement of the coordinate measuring machine, and measured coordinates are recorded. The switch device and the stylus can be realized as one complex of the probing system or they can be separated from each other. In the second case, the switch device and the stylus are connected with a magnet. Such realization of the probing system enables an automated replacement of the stylus which enables the fully automated measurements without any operator. The stylus is produced from synthetic flashing knob (alumina), zirconium dioxide, and silicon nitride. A special type of contact probing system is a scanning probe. The scanning probe sends to a controlling computer a continual list of data about the deviation of a stylus. During measurement, the stylus copies a surface of a measured object, and its trajectory is recorded into the controlling computer (scanning of the surface of the measured object). A new type of contact probing system is the probe for the measurement of surface roughness of the measured object. After the stylus of the probe touches the surface of the measured object, the stylus moves on the surface of the measured object along the defined profile, and deviations of stylus are measured. The result of the measurement is a profile of roughness presented by a line graph, which presents surface roughness in a cross-section (along with the measured profile). Laser scanning heads, industrial laser heads for distance measurement, camera probing systems, and special optical systems for measurement of components with a high quality of the surface realization belong to contactless probing systems. An advantage of these contactless probing systems is the possibility to measure objects with such surface which is not consistent enough or non-conductive or to realize measurements on moving objects. Laser probing heads are similar to terrestrial laser scanners and serve for nonselective measurement of geometrical shapes of the measured object (Fig. 7.4). The advantages of these probing heads are contactless measurement and their speed of scanning of the current heads (up to 200 thousands of points per second), which enables them to obtain a lot of measured data with high accuracy (several hundredths of millimeters). Laser probing heads are often installed on arms of industrial

7.5  Probing Systems of CMMs

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robots, where a position of the probing head is determined by a laser tracker. A combination of the polar CMM and robotic arm enables to integrate an inspection of components (also of the bigger objects) directly into the production line. Industrial laser heads for a distance measurement use a principle of laser trilateration or triangulation. They serve for distance measurement in the direction of one of the axes of the CMM. For instance, with a laser instrument for distance measurement oriented in the direction of the Z axis of the CMM (CNC instrument) it is possible to scan the surface of a measured component and then to create a 3D model. A coordinate of X and Y of the measured point is defined by a movement of the CMM; a coordinate of Z is measured by an instrument for distance measurement. Such realization of the probing system is mainly used by CNC working instruments. Camera probing systems consist of a CCD sensor and LED lighting of a measured object (Fig. 7.10). They enable optical measurements of objects of larger volume. To measure the objects’ geometrical parameters using the processing software (provided by a producer), the whole field of view or only a selected part can be used. Camera probing systems are used for the measurement of small components where a small stylus is not possible to use. They are also used for measurement of objects with a surface that has small consistence, for an inspection of boards of printed circuits (Hexagon 2016). Optical systems for measurement of components with the highly precise surface were developed for measurements of high accuracy and for a diagnosis of surface properties of measured components including roughness measurements of a surface and thickness of surface layers. Accuracy of such measurements is in sub-­ micrometer, whereby the measuring range is only several hundredths of millimeters.

Fig. 7.10  Camera equipped probing system (Renishaw 2015)

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7.6  Accuracy and Testing of CMMs The improvement of the CMMs and the increasing quality show the necessity of the definition of effective rules according to which would be possible to define the accuracy of CMMs. There are more possibilities of how to characterize CMM’s accuracy (Brezina 1987), (Kopáčik 1998). The easiest way is to characterize the accuracy of a CMM with one value, i.e., a maximum deviation of the CMM. The more effective way to characterize the CMM’s accuracy is based on a functional relationship between a final error (uncertainty) of the CMM and value of a measured distance (coordinates). According to this concept, CMM accuracy is given by the following formula (Brezina 1987):

σS = a + b ⋅l j.

(7.1)

This formula is similar to that one in geodesy which describes the accuracy of a measured distance by EDM, where σS is a standard deviation, which will not be overcome with the probability of 95% by meeting certain criteria. Element a is a constant denoting an influence of random errors of the coordinate measuring machine, b is a constant denoting an influence of systematic errors which are not excluded of the coordinate measuring machine, l is a measured distance (a measured parameter in a direction of one CMM axis), and j is an exponent with values of 1 or 0.5; it depends on conditions and the type of the coordinate measuring machine. The formula (7.1) describes the accuracy of a measured distance in the direction of the CMM axes. For practice, it is more useful to characterize the CMM’s accuracy by using the accuracy of a spatial distance (distance between two points in space). This type of accuracy is called global/total accuracy, and characteristics used for its description are called global/total characteristics of accuracy. In practice, there are often tasks, where it is necessary to measure distances on cylindrical or spherical surfaces. In those cases, the accuracy of results is described individually for each type of task (error models are prepared for a certain measuring task). Accuracy of the coordinate measuring machines is predominantly influenced by a realization of moving elements and the measuring system of the CMM. Errors of CMM’s measuring system are mainly caused by imperfection of a scale production (scales for distances and angles), during their installation, or by errors of the equipment used for interpolation. Moving parts of the CMM should move in lines in a space, but they move in curves (their trajectory is not straight-lined). This curvature of guidance surfaces of the CMM causes uncertainties in a determination of distances (coordinates) in the direction of each coordinate ax. These uncertainties arise because of an infringement of Abbe’s principle (a measured parameter and a scale have to lie on one line), as a consequence of the infringement of this condition about the mutual perpendicular position of the CMM axes and torsion of its moving elements (Kopáčik 1998). Uncertainties of the probing system of the coordinate measuring machine are caused by imperfection of its own probing system as well as by deviations of the shape of probing elements and their deformation by contact with the measured object. By contactless probing systems, these uncertainties are caused mainly by an error of the laser instrument used for distance measurement. By camera systems, it is caused by an error of optical system (magnification, distortion, etc.), similar to cameras used in photogrammetry.

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Various error influences and differences from the ideal geometrical conditions in the construction of the CMMs cause their accuracy to vary during their operation (accuracy characteristics of the machine change after a certain time) and their dependence on the position is limited. Accuracy of the CMMs is determined by their proof and testing. Methods and processes for CMM testing can be divided into two basic groups (Brezina 1987): • Uncertainty tests  – determine the uncertainty of individual components of the CMM, • Acceptance tests – verify the performance of the CMM using etalons and test artifacts (also known as global tests). For the correct determination of the uncertainty of the CMM components, it is important to apply the following rules during the test (Brezina 1987): • Stable thermal conditions should be established during the CMM testing (max. temperature changes could not reach 0,5 °C/hour), and at the same time the relative humidity, velocity, and vibration of the airflow should be registered. • The CMM should be operated by the operator. • The origin of the CMM’s coordinate system should be without any drift. • Measures used during the test should be certified, and their uncertainty should be 0.3 times higher as the required uncertainty for the tested components. • The test scope and content should be given by standards for the CMM testing and according to the type of the CMM. • All test results should include information about the test uncertainty. For the uncertainty test linear or angle portable measures are used, which are completed by test equipment enabling effective execution of the whole test procedure. The most often used measures are interferometers, autocollimators, telescopes, inclinometers, electronic levels, division tables, scales, and optical polygons. For testing of CNC machines and CMMs of lower accuracy, laser trackers could be used. Performance tests of CMMs did not need the fulfillment of all requirements given for uncertainty tests. By global testing, no detail and position determined values of errors are obtained, but only global information about the CMM’s accuracy is obtained. The main advantage of global testing of the CMMs is the simplicity and the connection to the generally solved tasks. When global methods of testing are used, physical measures (distance and angle), geometrical shapes, testing figures are applied. These are located in a working space of the CMM according to certain conditions (Kopáčik 1998). Etalon for the testing of the CMMs is presented by a solid figure, which withstands flexible deformations and is able to keep its parameters and shape without any significant (measured) changes during a long time period. Testing etalons are therefore produced from materials such are tool steel, invar, fused silica, natural stone, etc. Etalons consist of the set of spatially located simple geometrical elements (primitives) and their mutual combinations (Fig. 7.11). An ambition of producers and users of CMMs to unify the evaluation of CMM’s accuracy (characteristics) led to the creation of standards that should specify all important data about the CMM and testing methods. The whole series of ISO standards deal with the CMM testing (Table 7.1), which are mainly included in series of

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Fig. 7.11  Etalons and artifacts used in the performance test of CMMs

Table 7.1  ISO standards relevant to CMM testing Scope General

Relevant ISO standards ISO/IEC Guide 98-1:2009 Uncertainty of measurement – Part 1: Introduction to the expression of uncertainty in measurement ISO/IEC Guide 98-3:2005 Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) ISO/IEC Guide 99:2007 International vocabulary of metrology – Basic and general concepts and associated terms (VIM) ISO 14638:2015 Geometrical product specifications – Matrix model ISO 8015:2011 Geometrical product specifications – Fundamentals – Concepts, principles and rules ISO17450-1:2011 Geometrical product specifications (GPS) – General concepts – Part 1: Model for geometrical specifications and verification ISO17450-2:2012 Geometrical product specifications (GPS) – General concepts – Part 2: Basic tenets, specifications, operators and uncertainties ISO 3650:1998 Geometrical product specifications (GPS) – Length standards – Gauge blocks ISO 4287:1997 Geometrical product specifications (GPS) – Surface texture: Profile method – Terms, definitions and surface texture parameters ISO 5458:1998 Geometrical product specifications (GPS) – Geometrical tolerancing – Positional tolerancing ISO 5459:2011 Geometrical product specifications (GPS) – Geometrical tolerancing – Datums and datum systems (continued)

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139

Table 7.1 (continued) Scope Relevant ISO standards CMM testing and ISO 3274:1996 Geometrical product specifications (GPS) – Surface texture: verification Profile method – Nominal characteristics of contact (stylus) instruments ISO 10360-1:2000 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 1: Vocabulary ISO 10360-2:2009 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 2: CMMs used for measuring linear dimensions ISO 10360-3:2000 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 3: CMMs with the axis of a rotary table as the fourth axis ISO 10360-4:2000 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 4: CMMs used in scanning measuring mode ISO 10360-5:2010 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 5: CMMs using single and multiple stylus contacting probing system ISO 10360-7:2011 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 7: CMMs equipped with imaging probing systems ISO 10360-8:2013 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 8: CMMs with optical distance sensors ISO 10360-9:2013 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 9: CMMs with multiple probing systems ISO 10360-10:2016 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 10: Laser trackers for measuring point-to-point distances ISO 10360-12:2016 Geometrical product specifications (GPS) – Acceptance and reverification tests for coordinate measuring systems (CMS) – Part 12: Articulated arm coordinate measuring machines (CMM) ISO/PAS 12868:2009 Geometrical product specifications (GPS) – Coordinate measuring machines (CMM): Testing the performance of CMMs using single-stylus contacting probing systems ISO 15530-3:2011 Geometrical product specifications (GPS) – Coordinate measuring machines (CMM): Technique for determining the uncertainty of measurement – Part 3: Use of calibrated workpieces or measurement standards ISO/TS 15530–4:2008 Geometrical product specifications (GPS) – Coordinate measuring machines (CMM): Technique for determining the uncertainty of measurement – Part 4: Evaluating task-specific measurement uncertainty using simulation ISO 25178-601:2010 Geometrical product specifications (GPS) – Surface texture: Areal – Part 601: Nominal characteristics of contact (stylus) instruments (continued)

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Table 7.1 (continued) Scope Data processing/ interpretation of results

Relevant ISO standards ISO 1286-1:2010 Geometrical product specifications (GPS) – ISO code system for tolerances on linear sizes – Part 1: Basis of tolerances, deviations and fits ISO 1101:2012 Geometrical product specifications (GPS) – Geometrical tolerancing – Tolerances of form, orientation, location and run-out ISO 1660:1987 Technical drawings – Dimensioning and tolerancing of profiles ISO 1829:1975 Selection of tolerance zones for general purposes ISO 11562:1996 Geometrical product specifications (GPS) – Geometrical tolerancing – Surface texture: Profile method – Metrological characteristics of phase correct filters ISO 12181-1: 2011 Geometrical product specifications (GPS) – Roundness – Part 1: Vocabulary and parameters of roundness ISO 12181-2:2011 Geometrical product specifications (GPS) – Roundness – Part 2: Specification operators ISO 12780-1:2011 Geometrical product specifications (GPS) – Straightness – Part 1: Vocabulary and parameters of straightness ISO 12780-2:2011 Geometrical product specifications (GPS) – Straightness – Part 2: Specification operators ISO 14405-1:2010 Geometrical product specifications (GPS) – Dimensional tolerancing – Part 1: Linear sizes ISO 14405-2:2011 Geometrical product specifications (GPS) – Dimensional tolerancing – Part 2: Dimensions other than linear sizes ISO/TR 16015:2003 Geometrical product specifications (GPS) – Systematic errors and contributions to measurement uncertainty of length measurement due to thermal influences ISO 16010 series, Geometrical product specification (GPS) – Filtration ISO/TS 23165:2006 Geometrical product specification (GPS) – Guidelines for the evaluation of coordinate measuring machine (CMM) test uncertainty

ISO/TC213 Dimensional and Geometrical Product Specifications and Verification. The main group of these standards is represented by the ISO 10360 series, which specify two basic tests for the CMMs, the acceptance tests and the re-verification tests. The acceptance tests are used for verifying the performance of the CMM stated by producers. The reverification tests are used for periodically reverification of the CMM’s performance by users. Although there are series of ISO standards, which cover the topic of the CMM testing and verification, there are still CMM producers who specify characteristics for their CMMs in national standards, such as B89 (US) or VDI/VDE 2617 (German).

References

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References Brezina, I. (1987). Súradnicové meracie stroje a ich skúšanie. Prague: Vydavatelství úřadu pro normalizaci a měření. HEXAGON. (2015a). Leica Absolute Tracker AT 960. http://www.hexagonmi.com/de-AT/products/laser-tracker-systems/leica-absolute-tracker-at960. Accessed 20 Sep 2010. HEXAGON. (2015b). Romer absolute arm.. http://www.hexagonmi.com/de-AT/products/portable-measuring-arms/romer-gridlok. Accessed 10 Oct 2010. HEXAGON. (2016). Global line. Versatile coordinate measuring machines. http://www. hexagonmi.com/de-AT/products/coordinate-measuring-machines/bridge-cmms/global-classic. Accessed 10 Oct 2010. Kopáčik, A. (1998). Meracie systémy v inžinierskej geodézii (1st ed.). Bratislava: Vydavateľstvo STU. RENISHAW. (2010). Renishaw PH20. http://www.renishaw.com/media/pdf. Accessed 05 Oct 2010. RENISHAW. (2013). Renishaw OMP 40-2. http://www.renishaw.com/media/pdf. Accessed 05 Oct 2016. RENISHAW. (2015). Renishaw REVO 2 and RSP2 probes. https://www.renishaw.com/cmmsupport/knowledgebase/en/revo-2%2D%2D33018. Accessed 05 Oct 2016.

Chapter 8

Setting-Out and Measurement of Cranes and Crane Runways

Cranes are the basic tools for the movement of elements of equipment and products in industry or at the construction site. According to the shape and functionality, there are plenty of cranes. For safety use, it is very important to have their regular check and rectification. The chapter brings the basic classification of cranes, the basic requirements of their safe operation, as well as the methodology of geodetic measurements used during their setup (installation) and verification. The data processing part of the chapter includes the process of the final assessment of the controlled crane according to the international standards. The last part of the chapter brings information about the possible automatization of the crane measurement.

8.1  Basic Terms and Definitions Cranes are equipment used for take-up and handling loads in the given area (space) defined in horizontal as well as vertical direction. Cranes are important operating devices mainly in industry and at construction sites. Due to the hard operation load, they must be resistant to hard-wearing. In case of hard-wearing of crane rails or the crane, their operation must be stopped, which leads to production breaks and economic losses. To prevent this situation and the hard-wearing of the crane or crane rails, regular control measurements during their operation should be realized to determine the current state of the crane and actual geometry of rails. During the construction of the crane and the rails (runway), surveying methods are used for setting-out and the geometry control. Due to safety reasons, rails and the crane which are in operation has to be stopped during control measurements. The length of the crane operation break depends on the type of crane, length of the crane runway, required accuracy, and used measuring instruments. Respect and fulfillment of all safety regulations during the whole process are very important. Common control measurement takes generally several hours. © Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_8

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The required accuracy of the measured elements requires the improvement of used methods and technology. Nowadays, the classic method of alignment and leveling is replaced by a 3D polar method based on the use of total stations of higher accuracy. Application of the polar method decreases the length of necessary operation breaks but cannot eliminate them, as well as cannot eliminate the movement of the measuring personnel on the crane runway. The complexity of the measurement, as well as higher safety risk during the realization of these measurements led in the past to efforts to make these measurements partly or fully automated. This chapter brings an overview of existing technologies, which enables the realization of control measurements without the necessity of personnel movement on the crane runway. Crane is defined as an equipment for cyclic operation, for take-up, and handling of loads. Crane runways are built by the construction which is carrying rails. Rails enable the movement of a crane, a bridge, and a hoist (lifting component). The crane runway consists of: • Beams, crossbeams, girders, protecting cases, rails, and connecting elements • Pillars, basements, and supporting elements • Completing elements (benches, cable trays, railings, and ladders) Crane runway section is the continual (nondetached) part of the runway used for movement of the crane and the hoist (lifting component) using wheels. The crane runway field is a part of the runway section between two adjacent pillars (supporting elements). This could be outlaying, inside, or dilatating. The outlaying field can exceed the pillars at the end of the runway. Crane runway field span is defined by the horizontal distance of vertical axes of the adjacent pillars. Crane rail span (gauge) is the horizontal distance between the longitudinal axes of two appertaining beams or rails. Most of the crane runways have defined the rail span as the multiple of 300 mm. In case this cannot be realized, the span is determined as the multiple of 100 mm. Crane runway height is the vertical difference between the top of rails and the base plane of the crane construction usually defined by the crane reference point. Crane runway length is the distance measured between protecting cases (stops) made at both ends of the runway. Crane rail is the connection between the crane and the runway beams. It is the most loaded part of the crane runway. It is loaded mainly by hard-wearing, vertical and horizontal pressures (forces) produced by crane wheels during the crane operation (movement). The geometry (volume and shape) of the rails is designed according to the shape of crane wheels, the pressure (forces) produced by wheels and crane movement velocity. Crane rail axis is the line connecting the rail central points (centers) defined on the level of the rail top.

8.2 Classification of Cranes

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Protecting case (stop) is the rigid (fixed) element of the crane runway, which stops the crane at the end of the runway and protects the crane against accidents during its operation. Crane velocity is defined as the crane movement velocity measured during its stable continual movement with a maximum load. The velocity of the wind measured at 10 m above the terrain should be smaller than 3 m/s during the test.

8.2  Classification of Cranes Cranes are classified according to their duty and mobility as well as their operation conditions (number of operation cycles and the proportional load). According to the crane construction (shape), duty, and mobility, there are: • • • • • •

Bridge cranes Portal (gantry) and semi-portal cranes Cantilever/console cranes Tower cranes Mobile (road, railway, floating) cranes Special cranes

Bridge cranes belong to the most broadly used type of cranes in the industry. The crane construction is created by a bridge (bearing structure), which is moving on the crane runway built by two elevating rails (runway sections) and the moving part of the crane including crane wheels. The bridge could be created by a single or double girder bearing structure. A crane truck with the hoist (lifting component) and the load are moving on the bridge. The bearing structure of portal (gantry) cranes is built by the gantry, which consists of a crane bridge and two supports (legs) with the moving part positioned at the height of the crane runway (Figs. 8.1 and 8.2). The bridge could be without overlaid beams or could have an overlaid beam at one or both ends. The ability to carry the load in any direction is given by gantry supports, from which of one is fixed and the second has a pendulum bearing form. The main task of it is to eliminate lateral dynamical effects of the crane bridge due to the load operation. In the case of gantry cranes with gauge up to 15 m, the robustness (rigidity) of the structure enables the use of two fixed supports (Remta et al. 1975). The semi-gantry cranes are specific cranes. Their bridge is at one side set up directly on the rail and on the other side is set up on the rail through a support (leg) – Fig.  8.3. The first runway section is elevated, in most cases to the height of the bridge. This section is supported by the construction of the hall (building) or could have its own separate abutment wall. Cantilever (console) cranes are moving along the walls of the hall on runways installed and fixed to the hall wall (Fig. 8.4). The load in vertical direction brings over the wheels to the rail. The crane’s stability (elimination of the applied moment)

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Fig. 8.1  Semi-gantry crane with truck

Fig. 8.2  Gantry crane with two overlaid ends (consoles)

is given by beams installed over and under the crane rail. The crane construction is leaned against these through horizontally or vertically positioned wheels. The construction of the cantilever cranes consists of a vertical frame and a crane boom. The vertical construction of tower cranes is built by a simple bar (column) or by latticework. Tower cranes are commonly known as construction cranes. Crane runways in case of gantry, semi-gantry, and tower cranes consist of two sections (rails), of which relative position is given by the type and the construction of the crane. Crane runways can be installed for a long time in case of bridge, gantry, semi-gantry, and cantilever cranes or for a short period of time in case of the tower and mobile cranes at construction sites. Runways installed for a long time can be situated on (Ferjenčík et al. 1982): • Rigid base (mostly concrete base on the floor level) • Beams from their lower side (hanging or suspended cranes)

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Fig. 8.3  Semi-gantry crane

Fig. 8.4  Cantilever crane with a fixed boom

• Bearing structure which brings over the vertical and horizontal load to the supports situated in given distances (bridge or semi-gantry cranes) • Walls (cantilever cranes) • Separate construction – mostly situated outside of halls For operation conditions (number of operation cycles and the proportional load) are used different classification schemes. The ISO 4301-1 standard introduces a classification of hoists (applicable for all types of cranes) based on the maximum load, the number of operation starts, and maximum running time per hour (Table 8.1). The cross-referencing of two factors defines the right class of the hoist, which should be applied. The Crane Manufacturer Association of America (CMAA) introduced the classification for bridge and gantry cranes, which classifies cranes according to the maximal load and number of cycles (Table 8.2). Due to different approaches used for classification of cranes, their comparison can be very helpful for users. Table 8.3

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Table 8.1  Hoist classification by ISO 4301-1 State of loading Light Subjected very rarely to the max. load and normally to light load Moderate Subjected fairly frequently to the max. load but normally to rather moderate loads Heavy Subjected frequently to the max. load and normally to loads of heavy magnitude Very Subjected regularly to the max. load heavy

Total duration of use in hours 200 400 800 1600 3200 6300 12,500 – – M1 M2 M3 M4 M5 –

M1 M2 M3

M4

M5

M6

M1 M2 M3 M4

M5

M6

–

M2 M3 M4 M5

M6

–

–

Table 8.2  Classification of cranes by CMAA Class Usage A Standby or infrequent service B Light service

Lifts per hour 0–2 2–5

C D

Moderate service Heavy service

5–10 10–20

E

Severe service

20+

Typical workload Precise handling, slow speeds, used only occasionally Loads vary from no load to occasionally full rated loads, slow speed Average load is 50% of rated load Continuously handled 50% average load, lift the max. capacity with 30% frequency, faster speed Continuous use at/or near capacity, continuously lifts at the max. capacity, faster speed over class D

brings a comparison of classes defined by ISO, CMAA, the Hoist Manufacturers Institute (HMI), and the European Federation of Material Handling (FEM).

8.3  Crane and Crane Runway Parameters The next part of this chapter describes geometrical parameters and requirements of runways of bridge, gantry, and semi-gantry cranes, which are typical for industrial halls and plants. Requirements for tower, column, and hanging cranes are different and not discussed in this chapter. Bridge, gantry, and semi-gantry cranes are moving on rails situated on the rigid base (at the floor level) or on construction supporting the runway structure (over the floor). The aim of control measurements is the determination of relations between crane rails (runway geometry), protecting cases (stops), crane wheels as well as the geometry relation between the rails situated on the bridge or gantry, which are used for the crane truck movement. The main requirements are given for the runway geometry, which describes the lateral and the vertical position of crane rails and the rail span in the given sections.

8.3 Crane and Crane Runway Parameters

149

Table 8.3  Corresponding classes for crane and hoist determination Hoist classification ISO FEM HMI M2 1Cm H1 M3 1Bm H2

Crane classes CMAA A B

M4 1Am

H3

C

M5 2m M6 3m M7 4m

H4 H4 H4 or H5

D D D or E

Typical use Maintenance crane in machine house, used only occasionally Light-duty work crane, single operation, low average load, max. load lifted occasionally Medium-duty work crane, single operation, medium average load, max. load lifted occasionally Heavy-duty crane, regular medium and heavy loads Medium/heavy-duty work crane, nominal load regularly lifted Very heavy-duty crane, grab or magnet below the hook, regularly heavy loads

The lateral position of the rail is defined through lateral deviations of the longitudinal rail axis from the reference line, which belongs to the crane reference frame. Parallel to these, the rail connections, where the dimension of nonperfections is determined in the lateral direction, are controlled. The vertical position of the rail is defined by vertical deviations of the rail top (head) from the reference plane in the given sections. Parallel to this is determined the vertical deviation of the rails in each section. The reference plane is generally defined by the designed position of the railhead. In the case of old cranes, when the use of the designed reference plane position leads to large corrections and through this the rectification of the rails would be very expensive, the highest point of both rails could be chosen as a reference. Crane rails, which are in the correct position, must meet the basic geometry requirements: • • • •

Longitudinal axes of the rails are parallel. Railheads are in the same height. Rail span is equal with the distance measured between the crane wheel axes. Connection line of protecting case faces is perpendicular to longitudinal rail axes. • Longitudinal rail axes are perpendicular to rotating axes of crane wheels. Additional requirements define the relation between crane rails and crane wheels, as well as the relation between rails used for the movement of the crane truck: • Axes of the bridge (gantry) beams are perpendicular to the longitudinal axis of the runway. • Longitudinal axis of the crane wheels and the longitudinal rail axis are parallel. • Longitudinal axes of the rails and the truck are perpendicular to each other. • Longitudinal axes of the truck rails are parallel. • Truck rail span is equal with the distance determined by the axes of the truck wheels.

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8  Setting-Out and Measurement of Cranes and Crane Runways

• Connection line of protecting case faces of the truck rails is perpendicular to the longitudinal truck rail axes. • Top of the rails of the truck is in the same height.

8.4  M  ethods of Setting-Out and Measurement of Cranes and Crane Runways Cranes belong to industrial equipment, of which construction and operation require respecting a set of safety regulations and regular conditions (status) check. The crane operator is responsible for ensuring regular control measurements. During the construction, there are controlled parameters of the crane structure in given construction phases as well as at the end of the construction. The final check of geometrical parameters (final assembly test) of the crane and the crane rails (runway) is made by geodetic methods. Cranes, as mechanical engineering equipment operating on rails, demand high requirements for quality of all measurements made during their assembly and construction. These measurements are realized by surveying methods of high accuracy, generally known and used in the field of engineering surveying. The selection of the appropriate method is based on limits (maximal deviations) given for the construction, assembly as well as the setting-out of cranes and crane rails. These could be defined by the designer or according to international or national standards for cranes (Table 8.4). The crane rails are generally fixed on concrete or steel girders (beams), which are mounted on consoles of concrete or steel pillars. The surveyor’s workflow is applied according to the technology of assembly and is actually adjusted to the requirements of the company responsible for construction and assembly. The setting-out and construction of the crane runway require completion of the following tasks: • Preparation of setting-out drawings • Setting-out of the base of pillars (columns) or the supporting construction both the position and the height • Erection of pillars and columns • Setting-out and checking of pillar’s and column’s positions, height, and verticality • Assembly of girders (beams) and steel plates for rails on their top • Setting-out of rail axes on the beams both in the lateral and vertical direction • Assembly of the rails • Checking of position and height of rails • Creation of the as-built documentation • In-service setup

8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways

151

Table 8.4  Standards relevant to the bridge and gantry cranes Scope General

Design

Relevant standards ISO 4301-1:2016 Cranes – Classification – Part 1: General ISO 4301-5:1991 Cranes – Classification – Part 5: Overhead traveling and portal bridge cranes ISO 4306-5:2005 Cranes – Vocabulary – Part 5: Bridge and gantry cranes ISO 10972-1:1998 Cranes – Requirements for mechanisms – Part 1: General ISO 10972-5:2006 Cranes – Requirements for mechanisms – Part 5: Bridge and gantry cranes EN 12077-2:1998+A1:2008 Cranes safety – Requirements for health and safety – Part 2: Limiting and indicating devices EN 14492:2019 Cranes – Power-driven winches and hoists – Part 2: Power-­ driven hoists EN 15011:2011+A1:2014 Cranes – Bridge and gantry cranes ISO 4302:2006 Cranes – Wind load assessment ISO 4304:1987 Cranes other than mobile and floating cranes – General requirements for stability ISO 8686-1:2012 Cranes – Design principles for loads and load combinations – Part 1: General ISO 8686-5:2017 Cranes – Design principles for loads and load combinations – Part 5: Overhead traveling and portal bridge cranes ISO 11031:2016 Cranes – Principles for seismically resistant design ISO 11660-5:2001 Cranes – Access, guards and restraints – Part 5: Bridge and gantry cranes ISO/TR 16880:2004 Cranes – Bridge and gantry cranes – International standards for design and manufacturing requirements and recommendations ISO 16881-1:2005 Cranes – Design calculation for rail wheels and associated trolley track supporting structure – Part 1: General ISO 17096:2015 Cranes – Safety – Load lifting attachments ISO 17440:2014 Cranes – General design – Limit states and proof of competence of forged steel hooks EN 1991-3:2006/AC:2012 Eurocode 1 – Actions on structures – Part 3: Actions induced by cranes and machinery EN 1993-6:2007 Eurocode 3 – Design of steel structures – Part 6: Crane supporting structures EN 13001-1:2015 Cranes – General design – Part 1: General principles and requirements EN 13001-2:2014 Crane safety – General design – Part 2: Load actions EN 13001-3-1:2012+A2:2018 Cranes – General Design – Part 3–1: Limit States and proof competence of steel structure EN 13001-3-3:2014 Cranes – General design – Part 3–3: Limit states and proof of competence of wheel/rail contacts EN 13001-3-4:2018 Cranes – General design – Part 3–4: Limit states and proof of competence of machinery – Bearings EN 13001-3-5:2016 Cranes – General design – Part 3–5: Limit states and proof of competence of forged hooks (continued)

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8  Setting-Out and Measurement of Cranes and Crane Runways

Table 8.4 (continued) Scope Control/ inspection

Relevant standards ISO 7752-5:1985 Lifting appliances – Controls – Layout and characteristics – Part 5: Overhead traveling and portal bridge cranes ISO 8566-5:2017 Cabins and control stations – Part 5: Overhead traveling and portal bridge cranes ISO 9374-5:1991 Cranes – Information to be provided – Part 5: Overhead traveling and portal bridge cranes ISO 9927-5:2017 Cranes – Inspections – Part 5: Bridge and gantry cranes, including portal and semi-portal cranes and their supporting structures ISO 10245-5:1995 Cranes – Limiting and indicating devices – Part 5: Overhead traveling and portal bridge cranes ISO 12488-1:2012 Cranes – Tolerances for wheels and travels and traveling tracks – Part 1: General ISO 20332:2008 Cranes – Proof of competence of steel structures ISO 22986:2007 Cranes – Stiffness – Bridge and gantry cranes EN 1090-1:2011 Execution of steel structures and aluminum structures. Part 1: Requirements for conformity assessment of structural components EN 1090-2:2018 Execution of steel structures and aluminum structures – Part 2: Technical requirements for steel structures EN 12644-1:2001+A1:2008 Cranes – Information for use and testing – Part 1: Instructions EN13155:2003+A2:2009 Cranes – Safety – Nonfixed load lifting attachments EN 13557:2003+A2:2008 Cranes – Controls and control stations EN 13586:2004+A1:2008 Cranes – Access

Note: This table includes a selection of international (ISO) and European (EN) standards relevant to design, construction, and control of the bridge, gantry, and semi-gantry cranes

Control of the crane runway geometry can be done when required from the provider, as a requirement after the crane inspection results or according to the decision of the safety inspectorate. The reason for the control measurement is: • Control of the fulfillment of limits given by relevant standards • Collecting of information for determination of the reason for the crane or crane runway defects • Collecting of information for the runway reconstruction (repair) • Collecting of information for rail rectification The measurement consists of the definition of the reference frame including determination of their parameters, measurement of position, and span of crane rails, as well as the measurement of the crane geometry. The reference frame builds a basic structure for dependable determination of runway geometry and partly of the crane, too. Before the development of the crane’s reference frame, different aspects should be taken into account, for example, the crane type, its length, measuring equipment, and the required accuracy. The most often used configuration is a combination of two measuring (reference) lines, eventually a simple line (Figs. 8.5 and 8.6).

8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.5  Measuring lines in a parallel position adjusted to the rail endpoints

Fig. 8.6  Measuring lines connecting the rail endpoints

153

154

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.7  Polygonal reference frame

Fig. 8.8  Triangular chain in general position

In the case of very long crane runways or runways with large spans, we could use the polygon (Fig. 8.7) or triangular, eventually tetragonal chain (Figs. 8.8 and 8.9). The selection of the reference frame, its shape, and position in relation to rails is determined by the relations in a hall (environment), where the crane is installed (limitations due to production, the crane’s supporting structure and more). In the case of large cranes with a runway of special structure (doubled rails, runway length over 200 m, etc.) and extra maximum load, a special reference frame designed in a form of special geodetic network (Fig. 8.10) is required. This kind of network is generally used in mechanical engineering, where extreme accuracy and stability are required. According to their limited volume and distances between network points not exceeding 50 m, these are known as micro-networks (see Chap.. 4). Parallel to limitations in volume, there are high-accuracy requirements formulated for the network

8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways

155

Fig. 8.9  Tetrangular chain in general position

Fig. 8.10  Reference frame in a form of micro-network

points. They could reach the level of 0.1 mm in the variance of their coordinates. Typical application of such micro-networks is machine halls, power plants, cranes designed to heavy load, etc. The use of micro-networks enables multiple determinations of all measuring points on the crane rail as well as achievement of high accuracy in determination of their position. Before measuring the crane runway, rails are divided into sections; the measuring points are marked on the top of the rail – in their center – using special scissors and a center punch (Fig. 8.11). The distance between measuring points is chosen

156

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.11  Scissors for marking the rail center on their top (head)

according to the type and the structure of the crane runway with acceptance of the requirements formulated by the relevant standards. The position of measuring points on the rails, and by these the measuring profiles, are marked using calibrated steel tape with a millimeter scale. In the case of bridge cranes, the position of measuring points is chosen in vertical axes of the columns supporting the runway and in the middle between them. The measuring instrument is fixed directly on the rail using a special clamp (fixation) (Fig. 8.12) or outside of the rail, using a classical tripod or stands for pillars (Fig. 8.13). To achieve the requirements for the runway geometry, we evaluate separately horizontal (lateral) and vertical directions. To describe the runway geometry in the lateral direction, we use the deviation of the rail centerline from the measuring line determined for each section (profile). To describe the runway geometry in the vertical direction, we use the deviation of the centerline from the reference plane determined in each profile. Measurements necessary for the determination of the below-described deviations are realized in most cases separately by alignment, for determination of deviations in the horizontal direction, and by leveling for determination of vertical deviations. Parallel to modernization of the measuring technology as well as the increasing accuracy of measurements, the polar method is applied today, which allows common determination of deviations in both horizontal and vertical direction. During the realization of the measurement, the crane is fixed in the end position (Fig. 8.22). This way, it is not possible to make the measurement of the complete runway (rail). Measurement of this part will be made after finishing the measurement on both rails (the part accessible) and then, we move the crane in the opposite position. If the measuring (reference) line is chosen as the connection of two rail center points, it should be defined by two points accessible during the whole mea-

8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways Fig. 8.12 Instrument fixation on the rail using a special clamp

Fig. 8.13  Instrument setup using the stand for pillars

157

158

8  Setting-Out and Measurement of Cranes and Crane Runways

surement. In case, when the measuring line is chosen in general position (outside of the rails), it is necessary to take into account the minimum offset from the rail by their setup (according to the structure of crane wheels, brakes, etc.). The measurement of rails starts with the measurement of the main section – generally marked as an “A” section. After the instruments’ setup and their orientation along the measuring line, we start the measurement of deviations using the horizontal scale. The scale is set to the measuring point in each profile horizontally and the deviation is determined by direct reading in the instrument telescope (Fig. 8.14). In the case of points with a distance higher than 50 m from the instrument, a special scale with a moving target is used – for determination of deviations (Fig. 8.15). The person operating the scale is moving the target in the lateral direction to the point when the target is aligned to the measuring line and makes the reading directly on the scale. After finishing the measurement of the section “A,” we continue with the measurement of the section “B.” A necessary part of the measurement of crane rails is the measurement of the rail span, which is required to be done at least in three profiles – in the first, in the last, and in runway middle. For determination of the rail span, we use classical tape measurement, with calibrated steel tape. During the measurement, the tape is tightened with the same force as was used by the tape calibration. This is controlled by using a force balance. During data processing, corrections from the tape’s nominal length, the different temperature and the tape sag (deflection) are being applied. To measure the rail span, we can use different handheld distance meters, but their accuracy should be checked before they will be applied. Next, we need to determine the relationship between runway stops. Predominantly we focus on the position of the connection of their faces, which should be perpendicular to the longitudinal ax of the runway. To check this relation, the face of each stop is vertically projected to the rail top, and the distance between the projected point and the nearest measuring point on the rail is determined. This could be then measured by tape at the rail top and parallel to the measuring line. Fig. 8.14  Application of the scale in the horizontal position

8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways

159

Fig. 8.15  Application of the scale with moving target

All the measurements are made near the railhead and often along walls in the hall. This causes that most of the measurement is realized in conditions, which are affected by refraction in the vertical as well as the horizontal direction. To minimalize this effect, it is necessary to shorten the measuring distances, eventually divide the runway to more sections, if necessary. The connection of sections is controlled by the measurement of a minimum of 2–3 common points. The geometry of the rails is defined in vertical direction by deviations of the rail top (head) from the reference plane determined in the given profiles. The reference plane is given by the designed level of rails or by the height of the highest measuring point on the runway. Using the determined vertical deviations, we calculate the inclination of the rail in the longitudinal direction for each section given by adjacent measuring points. For the determination of the vertical deviation and the inclination of the rail in given points and sections, we use the classical leveling method (Fig. 8.16). During the measurement, the instrument can be set up directly on the rail using a special

Fig. 8.16  Rail measurement using precise leveling

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8  Setting-Out and Measurement of Cranes and Crane Runways

clamp or using tripods. The instrument position is chosen in the runway middle on the rail with better accessibility. The leveling staff (scale) footage should be completed by a special appliance, which ensures the precise position of the rod on the rail (Fig. 8.17). The maximum distance between the instrument and the rod is given by requirements (limitations) of the used measuring method as well as by environment (dust nuisance, the vibration of the air or the base, etc.), in which the measurement is performed. In that case, the runway is measured in sections in which connection should be ensured by the measurement of overlapping points. The last years’ development of total stations brought a possibility to make the runway measurement by the 3D polar method. Total stations and prisms of higher quality are used for the determination of the 3D position of points on the rail. For this kind of measurement are appropriate instruments with a standard deviation of angle measurement at the level of 0.5 mgon and distance at the level of 1–2 mm (Hánek and Buršíková 1993). The advantage of this method is a relatively free choice in instrument positioning, their possible setup on the floor (in most cases) and in the middle of the runway. The number of necessary instrument stations depends on the runway length, taking into account that the required accuracy may be achieved for distances up to 90 m (Hánek and Jirásková 2000). In the case of measurement using more stations, the connection of all measurements is ensured by a set of control (identical) points and appropriate transformation. The connection can be made also by using the same set of reference points determined before the measurement. The stability of the instrument during the whole measurement is controlled by observation to the same reference points at the beginning and after the measurement. The position of measuring points (center points of the rail) is determined by measurement to a mini prism, which is held directly on the point or is setting up in lateral direction using special appliance (Fig. 8.18). This is set up to the rail top in the horizontal position using the bubble and is fixed to the inner side of the rail. Fig. 8.17  Leveling rod with special appliance

8.4 Methods of Setting-Out and Measurement of Cranes and Crane Runways

161

Fig. 8.18  Special appliance for prism setup

According to the results of test measurement, authors declare uncertainty of repeated setup of the appliance by 0.2 mm (Hánek and Buršíková 1993). In the case of runway, which is on the floor level, the prism is held over the point by the measuring personnel (Fig. 8.19). Not only by the geometry of rails but also by the geometry of the crane and crane wheels, during the crane operation, should be controlled regularly. Mainly in case of cranes with large rail span or with heavy load is the measurement of the crane geometry necessary. In ideal conditions, the basic requirements formulated in Sect. 8.3 must be ensured during the crane movement on the rail. Besides these parameters, we control extra parameters on the moving parts of the crane, predominantly distances between wheel axes in different directions (Fig. 8.20). During these measurements, except for surveying instruments and equipment, we use various special appliances and mechanical engineering equipment applied to crane measurement. Fig. 8.19  Setup of the mini prism on the rail

162

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.20  Measurement of crane wheels geometry

The omission of regular checks of the crane’s geometry leads to increase abrasion and deformation of rails.

8.5  Data Processing and Analysis The aim of control measurements of cranes is to check the fulfillment of geometric requirements, which describe the current state of the crane runway and the crane. The crane rails should be in the designed position, given by lateral and vertical direction and by the rail span. Possible deviations from the designed position and shape are given by limits (tolerances). Their acceptance and fulfillment are necessary for the correct operation of the crane. The crane runway and crane, which do not fulfill these requirements (limits), should not be in operation and should be rectified. The calculation of values for rectification, e.g., values, which are necessary to know “in which direction and how much” should be the rail moved to reach the state fulfilling basic geometric requirements, will be a part of the data processing. During data processing, they are determined step by step: • • • • •

Parameters (coordinates) of reference points Parameters of measuring points on rails Crane parameters Rectification values in lateral direction and values for rails span rectification Rectification values in the vertical direction

8.5 Data Processing and Analysis

163

From the surveying point of view, reference systems (frames) of cranes have a simple structure that is often used in engineering surveying. It is important to determine all measurable values in the network with the required quality. The network point parameters are determined by adjustment (in most cases by the general least square method – LSM). Measurement and data processing of this kind of network belong to general surveying tasks, and it is not necessary to discuss this in detail at this point. The data processing of rail measurement, determination of lateral, and vertical deviations of measuring points are done according to the used measuring methodology (alignment and leveling or polar method). Accuracy requirements of determination of deviations are given by standards formulated in general in form of limits (tolerances), which reflect the operation load and geometry (length, rails span) of the crane runway and the crane (Table 8.4). Many case standards for design and production of steel structures are used for the evaluation of cranes and their runways. It is generally accepted, that the crane should be controlled and evaluated on the base of standards that were applied for their design. Many countries accept when the operator of the crane makes a decision to change the standard(s) for the crane evaluation when this leads to higher quality and safety in crane operation. An example of a set of requirements formulated by European standards EN 1090 and EN 1993 is in Tables 8.5 and 8.6. Crane which does not meet basic requirements for geometry should be set out of operation and it is necessary to make its correction  – rectification. Rectification values, which should be applied during rectification of the rails and the crane, are determined in each profile, both the lateral and vertical direction. In the past, to determine rectification values in the lateral direction, usually graphic procedures had been used. These started with graphic presentation of deviations and tolerance intervals in form of bands. Next, the optimal position of the rail was searched (constructed) inside the tolerance band separately for both rails. This kind of determination of rectification values lead to two lines, which could not be parallel, and therefore check of rail span (tolerance) in each profile was necessary (Lukáč and Kopáčik 1986). As an opposite of this method, we use different analytical procedures resulting in an exact solution. Most of these procedures use the classical LSM method, which after rectification “generates” rails in optimal and parallel positions. The optimal position of rails needs minimum effort (work) in the realization of rectification. The disadvantage of LSM application could be significant “rotation” of rails opposite to their designed position. Significant rotation of rails leads to a decrease in the bearing capacity. Applying tolerances (limits) for rectification values in lateral direction directly in the data processing procedure will set limitations (borders) for the significant rotation in the calculated rail position. Cranes are often measured in the local coordinate system defined by using the first and the last rail center point. In case when a separate coordinate system is defined for each rail section, these should be transformed into one common system before calculating rectification parameters (Fig. 8.21). Generally, we set the origin of the system and the “x” ax into the main rail marked “A.”

  ∆R = ± 5 mm   ∆R = ± 5 + [R − 16]/4 mm

Difference in the measured length 2 m

Difference in height  For R ≤ 10 m  For R > 10 m

Difference in span  For R ≤ 16 m  For R > 16 m

Height of the railhead/top

Difference of heights of the railhead in the given section

Rail span

Note: aValues exceeding tolerances (in the report are colored red)

  ∆h = ± 10 mm   ∆h = ± R/1000

To the designed/given height To the given level

Vertical deviations Depth of the crane beam of span L

∆ = ± 10 mm ∆ = ± L/1000 Ale |∆| ≥ 10 mm ∆ = ± 2 mm

Deformation on 2 m length

∆ = ± 1 mm

Maximum deviation Parameter Class 2 To the designed position-reference line p = ± 5 mm

Rail local deformation

Criteria Lateral deviations

Table 8.5  Crane runway evaluation according to EN 1090

 A3−B3 = −7.1*  A2−B2 = +5.7*

All in given tolerance

All in given tolerance

All in given tolerance All in given tolerance

Values exceed tolerances (mm) A11 = +6.3a A3 = −9.2a A1 = −5.6a B9 = +5.6a A2 = −1.1a

164 8  Setting-Out and Measurement of Cranes and Crane Runways

Rail span including temperature correction ΔR ≤ 10 mm

Lateral deviation δy ≤ L/600

Difference of heights of the railhead in the given section Δh ≤ R/600

Criteria Vertical deviation δz ≤ L/600 but δz ≤ 25 mm

Table 8.6  Crane runway evaluation according to EN 1993 Scheme

8.5 Data Processing and Analysis 165

166

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.21  Common coordinate system for crane measurement

Coordinates of measuring points will be determined by

(

)



(

)



yi = y1 + sti sin α12 + ki sin α12 ± 100 g ,



xi = x1 + sti cos α12 + ki sin α12 ± 100 g ,



(8.1) (8.2)

where y1 and x1 are coordinates of point 1. st is stationing of the point 1. k is lateral distance between the measuring point position and the measuring line. α12 is the direction of a measuring line. The rail span could be calculated using coordinates of the points measured in given profiles on both rails. In profiles, where the span is measured, we calculate the difference between the measured and the calculated span value. Finally, the mean value of the rail span is determined by n

R=



∑R

i

i =1

n

,



(8.3)

where Ri is the rail span in the given profile. n is the number of profiles measured on the runway. The optimal position of the rails will be defined by the common regression line Yi = θ 0 + θ1 . xi + ε i ,



(8.4)

where θ0 and θ1 are coefficients of the regression function. x are measured values. ε are random errors of measured values. Applying the Gauss-Markov rule of the minimum of the sum of squared residuals:

8.5 Data Processing and Analysis

167 n



∑ (Y − Y ) i

i

2

= min,

(8.5)

i =1

which has a simple and explicit solution. When Y is the vector of functions that describe the relationship between measured values and unknown parameters, the measurement was done with the same accuracy, and systematic errors were not present in the measurement (Anděl 2007)

Y = Aθ + ε

(8.6)

parallel will be



E [ Y ] = Aθ , E [ ε ] = 0, Σ Y = Σ ε = σ 2 I the rank of the matrix R [ Y ] = k, n > k



where n is the number of measured values. k is the number of unknown parameters – regression coefficients (k = 2). Y = (y1,   …  ,   yn)T is the vector of measurements is the design matrix, which elements depend on the regression function Θ = (Θ1,   …  ,   Θk)T is the vector of unknown parameters ε = (ε1,   …  ,   εn)T is the vector of random errors in the measurement σ2 is the measurement variation I is the unit matrix. ˆ , including Θ ˆ (shift) and Θ ˆ (direction) The vector of unknown parameters Θ 0 1 of the regression line, could be calculated as ˆ ˆ =  Θ1  = AT A Θ ˆ   Θ 2 

(



)

−1

AT Y,

(8.7)

where



 1 a1    1 a2  A= .       1 an 

The covariance matrix of the unknown parameters will be given by

(

Σ Θˆ = σ 0 2 AT A

)

−1

,



(8.8)

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where σ02 is sampling variance of residuals n



σ 02 =

∑v v

i i

i =1

(8.9)

. n−k

Using the covariance matrix Σ Θˆ we could calculate the variances of the unknown parameters

σˆ Θi = Σ Θˆ i ,i .

(8.10)



The vector of residuals (deviations of the measuring points from the regression line will be given by

ˆ = AΘ ˆ. vˆ = Y − Y

(8.11)

Using the covariance matrix of residuals



(

Σ vˆ = σ 2  I − A AT A 

)

−1

AT  

(8.12)

we can calculate the variances of residuals

σˆ vi = Σ vˆ i ,i .



(8.13)

The regression line calculated is given by

ˆ +Θ ˆ .x . Yˆi = Θ 0 1 i

(8.14)

The significance of regression coefficients is controlled by the statistical test. ˆ and Θ ˆ and is The zero hypothesis H0 is formulated in a form of coefficients Θ 0 1 equal to zero. In this case, these are not significant. The decision about the acceptance or nonacceptance of the zero hypothesis is based on the statistic ti =

ˆ Θ i , σˆ Θˆ i

(8.15)

which is compared to the critical value tn − k(α) of the student’s probability distribution with n – k degrees of freedom and the significant level α. In case of inequality

t i ≥ t n − k (α ) ,



(8.16)

8.5 Data Processing and Analysis

169

ˆ is accepted for the function. the zero hypothesis H0 is denied and the coefficient Θ 1 The simplest way for determination of parameters of the regression line is to use existing software with built-in functionalities. Followingly is an example of a calculation of rectification values using MS Excel. Coordinates of measuring points are calculated by formulas (8.1) and (8.2), the reference frame is given by the rail center points (A1, A13, B1 a B13 – Fig. 8.21) – see Table 8.7. Applying the function INTERCEPT (x, y) will be calculated Θ0 and using the function SLOPE (x, y), the coefficient Θ1 of the common regression line of both rails. Θ0 = INTERCEPT ( x,y ) Θ0 = 9.978 m Θ1 = SLOPE ( x,y ) Θ1 = 0.00008





The coefficient Θ1 defines the direction of the regression line according to the reference frame determined by Θ1 = tg (ϕ ) ,



(8.17)



which is the same for regression lines of both rails. The coefficient Θ0 will be determined to add/reduce this by half of the designed rail span (R/2 = 10.000 m). The equation for both rails will be formulated as. Rail“ A ” Rail“ B”



y = 0.00008 x − 0.022 y = 0.00008 x − 19.978

[m ] [m ]

Using these equations, we calculate the coordinates of the optimal position of measuring points. The rectification value of each point is calculated as the difference between the measured and the optimal position of this point. The rectification of the rail is done when the rectification value exceeds tolerances (limits) given by Table 8.7  Coordinates of measuring points Rail A

Rail B

Point A1 A2 A3 ↓ A13 B1 B2 B3 ↓ B13

x (m) 0.000 6.000 12.000

y (m) 0.000 −0.017 −0.006

144.000 0.000 6.000 12.000

0.000 20.003 19.980 19.971

144.000

20.003

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relevant standards. The mean value of the rail span is calculated using the formula (8.3) and is R = 20.004  mm. The determination of rectification values in vertical direction consists of the determination of differences between the measured values (heights) and the height of the reference plane in each profile of the crane runway

vHi = H ref − Hi .

(8.18)

As the reference plane, we generally choose the horizontal plane in the height of the highest measuring point (Href = Hmax). Height differences are determined with an accuracy of 1 mm. Parallelly we calculate the inclination of the rail in a longitudinal direction, using heights of the adjacent points, and transform it into percent. The rectification of rails is made by the underlying of the rail with steel plates in the given points. However, results of crane measurement are used beside surveyors also by experts of different professions. Visualization and interpretation of these results are very important. According to long-term experience, there are given rules for visualization of these in many countries (Lukáč and Juzwa 1991). Mostly is visualized the actual position of the crane runway in both directions (lateral and vertical), the rail span in each profile, and the rectified rail in both directions (Fig. 8.22). The drawing is completed by numerical values of deviations, rectification parameters (all in lateral and vertical directions), and rail span and inclination. The position of the rectified rail, including the numerical presentation of rectification values, is written in red color. An example of possible visualization of results including the rectification values brings the drawing in Fig. 8.23.

8.6  Automated Measurement of Rails For crane measurement and determination of the crane runway geometry, in the past were used explicitly optical surveying instruments (theodolites and levels). The new development came along with the use of laser-based instruments and equipment for surveying. This kind of instrument is not produced regularly, but several prototypes exist already nowadays. They are often generated as a result of research. The aim of this research is to minimalize the movement of the measuring personnel on the rails. One of the first prototypes was a trolley developed in the Research Institute of Geodesy, Topography, and Cartography in Zdiby (Czech Republic) with motorized driving and remote control (Lechner 1986). The trolley moves on rails and stops in each profile, where the reading on two scales (lateral and vertical) is done. Accuracy of the trolley positioning into the profile is 50 mm. The center position of the lateral scale is given by the trolley’s structure and driving, which is working on the principle of rail scissors. The measurement is made four times, each measurement in another direction, forward and backward to the theodolite mounted at the beginning of the rail. Using the trolley, there could be only lateral and vertical deviation of the

Fig. 8.22  Crane runway geometry and position (situation)

8.6 Automated Measurement of Rails 171

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.23  Deviations and rectification values of crane rails

172

8.6 Automated Measurement of Rails

173

rail from the determined reference line. The rail span is determined in a classical way, by using tape measurement. The application of this prototype does not eliminate the access of the measuring personnel on the rail. Using a motorized trolley and the polar method for determination of the rail geometry is described in (Arnold 1989). The theodolite station is chosen in the middle between the rails according to the rules for the application of the classical polar method (Fig. 8.24a). The remotely controlled trolley is moving on the rail with two prisms, which are mounted to the trolley that way so that it minimalizes the trolley’s inclination during the movement (Fig. 8.24b). The position of the measuring point is determined by using the measurement of both prisms by the trolley moving forward and backward. The advantage of this method is that it is not necessary to set out profiles on the rail, as well as the access of the personnel to the rail. Demag Crane & Components developed a laser measuring system (LMS) for automated measurement of crane rails a few years ago. The system consists of a laser, trolley, radio remote control, and computer. The laser, which emits visible beam and includes accumulators and switch with remote control, is fixed at the beginning of the rail (Fig. 8.25). The current version of the LMS performs automatic, three-dimensional surveys of crane runways, which take each measurement multiple times, resulting in accuracy better than 0.5  mm (Demag Crane & Components 2017). Intelligent sensors help to achieve this high level of reliability for all types of rails and also worn profiles. When the measuring process has been completed, the results are shown in real-time visualization. The main part of the system is the motorized trolley with a CCD, rail sensor, and data processing unit with A/D converter, motor, accumulator, and remote control

Fig. 8.24 (a) Reference frame and measuring points, (b) trolley with two prisms

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Fig. 8.25  Laser measuring system (Demag Crane & Components 2017)

(Fig. 8.26). The trolley is moving on the rail using the clamp with four wheels in the horizontal position and two wheels in the vertical position. The clamp with wheels enables the use of the system at different types and shapes of rails. The trolley movement is managed by a portable computer and remote control, which is appropriate for data collection, too. Data processing is based on the alignment method, where the reference line is realized by a laser beam. The trolley position along the rail is determined by the length sensor and the deviation of the measured point from the reference line is measured on the CCD as the laser beam deviation from the CCD center in both lateral and vertical direction. An automated measuring system based on the polar method was developed at the Department of Surveying of the STU in Bratislava (Slovakia). This system consists of a frame with sensors and prisms, mounted on the crane bridge or gantry (Figs. 8.27 and 8.28). The frame is mounted on the crane bridge in such position, which enables the contact of wheels with the rail from the top and from inside (Fig. 8.29). Values d and h are determined by the frame calibration. Other values describing frame geometry are given by the design and the assembly of sensors as well as the frame elements. Synchronized collection of data enables determination of the actual position of measuring points in time when polar coordinates measured by the total station are registered. Frequency of data collection is limited by the maximal registration fre-

Fig. 8.26  Motorized trolley (Demag Crane & Components 2017)

8.6 Automated Measurement of Rails

175

Fig. 8.27  Frame with sensors and prisms mounted on the crane bridge (Kyrinovič 2011) Fig. 8.28 Determination of the frame position using a robotic total station (Kyrinovič 2011)

quency of the total station. Due to this, the maximal number of measured points on the rail is limited and the distance between the two following points is given. The density of measuring points is then 3 mm to 5 mm, which results in 2700 points on each rail of the 100 m crane runway. Due to continuous measuring, the position of points varies up to 10 mm in both the lateral and vertical directions, which could be filtered using a Kalman filter (Fig. 8.30).

176

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.29  Determination of the measuring point position (Kyrinovič 2011)

According to the published experience, the standard deviation of measuring point coordinates achieves the level of 2 mm–3 mm (Kyrinovič 2011). Comparing the results of this method with the results of classical crane measurement, differences in the position of single points reached values up to 10 mm in the lateral direction and up to 5 mm in the vertical direction. Because the frame with sensors and prisms is fixed to the crane bridge, it moves along the rail together with the bridge. This solution enables to eliminate the personnel’s movement on the rail but another side of the bridge load affects the rail during

Fig. 8.30  Rail position in lateral direction before (gray) and after application of the Kalman filter (black) (Kyrinovič 2011)

8.6 Automated Measurement of Rails

177

Fig. 8.31  ARTIS monitoring vehicle on the rail (Dennig et al. 2017)

the measurement, which should be taken into account by data processing. The results published in (Kyrinovič 2011) confirmed the minimal impact of the crane bridge on the rail position in the lateral direction. In the vertical direction, a systematic impact had been documented, with deviations ranging from 0 mm to 4 mm. The development of an automated crane runway measuring system advanced rail track inspection system (ARTIS) is described in (Dennig et al. 2017). The system is used to measure the 3D position of crane rails, the cross-section of crane rails, joints, and, for the first time, (crane rail) fastenings. It consists of a monitoring vehicle and an external tracking sensor; and makes kinematic observations with the tracking sensor (laser tracker, total station) from outside the rail run, e.g., the floor of an overhead crane runway, possibly (Fig. 8.31). ARTIS is equipped with two profile laser scanners (PLS), two cameras, an inertial measuring unit (IMU), an inclinometer, and two odometers. The inclination sensor and the IMU are producing information about the ARTIS’s inclination, which is used for correction of the prism position (offset). The novelty in development is the use of camera images in connection to the data of PLS, which document the current state of the profile, of rail joints, and of fastenings (Fig. 8.32). Measurement uncertainty of the ARTIS system should be evaluated (1) from the point of view of position determination being 0.2 mm and (2) from the point of view of the determination of the rail profile (shape). The accuracy of the point position, with respect to the rail length of 110 m, is documented by the average position error of Helmert’s type, which achieves values between 0.28 mm and 0.36 mm. The relative accuracy of the rail profile determination could be described by the uncertainty of 0.16 mm (1σ) at a standard measuring range of 240 mm. Regarding the height information and their declared uncertainty, the smallest detectable change in rail height or shape is 0.23 mm.

178

8  Setting-Out and Measurement of Cranes and Crane Runways

Fig. 8.32  Rail profile determination using two PLSs (Dennig et al. 2017)

References Anděl, J. (2007). Statistické metody (4th ed.). Prague: Matfyzpress. Arnold, R. (1989). Eine neue Technologie für Kranbahnkontrollmessungen. Vermessungs-technik, 52–55. Demag Crane & Components. (2017). LMS crane measuring system. https://youtu.be/ erRSZ4412GQ. Accessed 6 Dec 2019. Dennig, D., et al. (2017). Comprehensive and highly accurate measurements of crane runways, profiles and fastenings. Sensors, 17. https://doi.org/10.3390/s17051118. Ferjenčík, P., et al. (1982). Kovové konštrukcie II. 1st part. Bratislava: Edičné stredisko SVŠT. Hánek, P., & Buršíková, O. (1993). Měření jeřábových drah totálními stanicemi. Geodetický a kartografický obzor, 81(1), 8–11. Hánek, P., & Jirásková, J. (2000). Znovu o měření jeřábových drah totálními stanicemi. Geodetický a kartografický obzor, 88(2), 21–25. Kyrinovič, P. (2011). Automatizované meranie geometrických parametrov žeriavových dráh (Research works). Bratislava: Slovak University of Technology, Faculty of Civil Engineering. Lechner, J. (1986). Měření geometrických parametrú jeřábových dráh při použití měřicího vozíku s dálkovým ovládáním. Geodetický a kartografický obzor, 74(5), 117–122. Lukáč, Š., & Juzwa, K. (1991). Aktuálne problémy geodetického merania žeriavových dráh. In 40 rokov Katedry geodézie SvF STU v Bratislave. Bratislava: SVŠT. Lukáč, Š., & Kopáčik, A. (1986). Analytické určovanie smerových parametrov žeriavových dráh. Geodetický a kartografický obzor, 74(6), 143–148. Remta, F., et al. (1975). Jeřáby. 2nd part (2nd ed.). Prague: SNTL.

Chapter 9

Setting-Out and Control of Rotary Kilns

One of the most used equipment in the production of materials for the building industry is the rotary kiln. Due to the big volume and high temperature, permanent deformations occur during the kiln operation. Considering these conditions, it is important to make regularly control measurements, mainly to check the fulfillment of the basic geometric parameters. These measurements are produced by the surveyors and based on geodetic methodology and instrumentation. The chapter brings the description of the equipment, their basic conditions for regular operation, as well as the methodology of measurements. For the operation, it is important to fulfill the condition mainly given for the kiln geometry, which is reached by the rectification of the kiln position and their supports. The methodology of calculation of the optimal rectification parameters is included in the chapter.

9.1  Conditions of the Correct Rotary Kiln Operation Rotary kiln is a pyro-processing cylinder form of technology equipment with closed, from the surrounding isolated working space, in which hot gases pass along usually in the opposite (sometimes in the same) direction as the direction of the process material is moving. Rotary kilns are used generally for drying, calcinating, granulating, and roasting of bulk materials (e.g., gypsum, bauxite, sulfur, etc.). As the kiln rotates, material gradually moves down toward the lower end and may undergo a certain amount of stirring and mixing. The rotary kiln structure consists of a steel cylinder shell, inside with refractory lining, setting up on a set of tire rides (tires) and support rollers (Fig. 9.1). Hot gases in rotary kilns may be generated in an external furnace or may be generated by a flame inside the kiln. According to the process requirements, the temperature inside the kiln may achieve 1500  °C.  The rotation velocity of the kiln should be constant and may vary between 0.5 and 2.0 rpm. It is necessary, that the kiln rotates very slowly, 0.25 rpm only, but should be never stopped due to possible © Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_9

179

180

9  Setting-Out and Control of Rotary Kilns

Fig. 9.1  Rotary kiln triads in operation (SMZ 2016)

temperature deformation of the shell and damage of the refractory lining. Kilns are designed according to the process requirements of various sizes and structures. Usually, they are within these parameters: • • • • •

Shell diameter from 2.2 m up to 6.0 m Length up to 250 m From 2 up to 5 tire rides Diameter of rollers between 1.0 m and 1.4 m Inclination of the kiln’s longitudinal ax is between 2% and 6% According to the shape and structure of the kiln this could have a form of:

• Cylinder with a constant diameter • Cylinder with broadened part in the middle • Cylinder with two broadened parts for material drying and roasting The shell is placed on tire rides on pairs of steel rollers and rotated using a classic gear train and a variable speed electro engine. The rollers must support the kiln, hold it in the given position, and allow its continuous rotation. The rollers are also machined to a smooth cylindrical surface and set symmetrical to a kiln’s vertical ax. The tire must snug fit the shell, but also allow thermal movement, which results in the use of a variety of fastenings between the tire and the kiln shell. The shell tournament makes possible the usage of steel tires, supporting roles, drive gear, and electro engine (Figs. 9.2 and 9.3). Roles are fixed to the base using roll-bearings and special steel support structure, which enables the rectification of the roller position in the horizontal direction. The roller inclination is rectified by

9.1  Conditions of the Correct Rotary Kiln Operation

181

Fig. 9.2  Rotary kiln structure (side view, nadir view) Fig. 9.3  Rotary kiln structure (cross-section)

underlying steel plates. The stable position of the kiln in the longitudinal direction is ensured by thrust rollers mounted usually on some of the tires. An important part of the kiln gearing is the gear ring and the pinion, which are in engaging movement to each other. The shell length and the shell diameter enlarge during kiln’s operation according to the height of the temperature (the temperature of the shell can achieve 350 °C). Tires and the shell change their form also due to the big load generated by refracting

182

9  Setting-Out and Control of Rotary Kilns

lining, the volume of the processing material, and the mass of the shell itself (the mass of a 60 m long kiln shell is about 730 tons). As a result of these changes, the position of tires on the rollers is changed, and the relation between the drive gear and the pinion, as well as the relation between the shell and tires, are changed, too. Due to possible settlement of base blocks, it could also change the absolute position of the rollers. All these changes and deformations lead to unequal abrasion of many construction elements of the kiln and, last but not least, they generate breaks in production. The assumption of correct kiln operation, the minimal load of the kiln construction parts, as well as minimal abrasion of tires and rollers need to fulfill the following conditions (Figs. 9.2 and 9.3): • Longitudinal ax of the kiln shell and tires should be aligned and have the given inclination (theoretical ax of the kiln). • Vertical plane defined by the longitudinal ax of the kiln should include center points of the corresponding pair of rollers. • Roller axes should be parallel and symmetric to the longitudinal kiln ax. • Kiln mass should be equally divided between the rollers. • Between thrust rollers and the tire it should be the given allowance to enable the compensation of thermal deformation of the shell and the tires in the longitudinal direction. • The allowance between the drive gear and the pinion should ensure correct gear mesh (between 1/4 and 1/6 of the gearing module). • Direction of roller axes (usually of the roller pair, which is on the same base with thrust rollers) should ensure a right and stable position of the tire between thrust rollers during the kiln rotation. Fulfillment of the below-formulated requirements is always controlled by geodetic measurement: • In case of kiln construction ev. its general repair • After regular repair of the kiln (during operation breaks) • When the position of the kiln is controlled during the operation (i.e., the heated kiln) Based on measurement results, we can determine rectification values (parameters). The application of these parameters ensures the right position and the correct shape of the shell, tires, and rollers, as well as optimal conditions for the kiln’s operation. Parallel to the determination of the actual position of the shell, their deformation (ovality) is also measured.

9.2  Geodetic Works Related to Rotary Kiln Assembly To ensure smart and correct realization of the measurement, it is necessary to take appropriate care to the preparation and coordination of all geodetic works. An important part of the agreement between the customer and the provider is a detailed

9.2  Geodetic Works Related to Rotary Kiln Assembly

183

time schedule of the measurement, in case of a simple one, as well as in the case of series of repeated measurements. The time schedule is made in cooperation with the kiln head technician, and it is applied after his/her acceptation. In the case of long-­ term measurements, the schedule is prepared for 1 year period. During the preparation of geodetic measurements, it is very important to have a good knowledge of the kiln design documentation and to pay attention to: • Exploration of the kiln and its surrounding • Control of all documents and other information provided by the customer • Disquisitional preparation of instruments and measuring equipment as well as the kiln surrounding • Ensuring all safety regulations and a safe workplace The ordering party, in cooperation with the head of the measuring group, ensures cleaning of the working space, of determined instrument stations, measuring points at the kiln, on the kiln basement as well as in the kiln’s surrounding. Followingly, tires, rollers, gearing, and the housing of rollers have to be cleaned and dismounted. The manufacturing of special equipment is being ordered in the case when they are necessary due to the specialty of the measured kiln or when it had not been ordered during former measurements  – tripods for roller’s height determination, screws for ax determination, etc. These belong to the kiln equipment and are usually kept by the kiln operating personnel. To ensure the safety of the workers and to prevent possible accidents, it is necessary: • To inform the kiln head technician about the time schedule of all measurements • To install over the shell a safety rope (ca in height of 1 m over the shell top) and ensure that all the workers and measuring personnel use safety belts and connect this to the rope during the measurements • To ensure that all workers and measuring personnel use respirators. Geodetic measurements are done using a reference frame of the kiln, which is defined as the local 3D Cartesian frame with the X ax in horizontal position and parallel with the longitudinal ax of the kiln and the ax Z in the vertical direction (Fig. 9.4). Fig. 9.4  Determination of the coordinate system

184

9  Setting-Out and Control of Rotary Kilns

The definition of the X ax parallel to the longitudinal ax of the kiln and shunted one side by the distance larger than the shell’s diameter half (usually into the reference plane defined for setting-out of the kiln) enables simple interpretation of deviations and the excess of limit values. Use of the reference frame in general position or exactly parallel with the kiln’s designed axes complicates the evaluation of measurements and the determination of rectification parameters. Points, which define the reference frame position and orientation are usually fixed and stabilized in the kiln basements or in their neighborhood. Measurement of heights refers to the horizontal plane defined approximately in the shell center (expressed with 0.1 m accuracy) – local horizon (level). In the case of the unexisting point of the state leveling network in the kiln’s surroundings, the height measurements are connected to this point. Measurement of height includes determination of control points installed on buildings in the kiln surrounding, on the kiln supporting construction near the upper and lower part of the shell, and on the kiln basements (Fig. 9.5). It is recommended during construction and montage to set up steel plates on the kiln base top. These are used for marking the reference line (vertical projection of the reference plane) which is parallel with the kiln longitudinal ax. The position of the reference line is marked by holes on the steel plates, to enable: • Measurement of horizontal distances of the measuring points to the reference plane in the height of the rollers’ axes and the rollers’ support • Fixation of marks, which signalize the reference line position on the kiln basement as well as prolongation at both ends of this line • Optimal choice of instrument positions The kiln’s construction starts with setting-out of the kiln base using geodetic methods. The setting-out works are done according to kiln documentation (design) and relevant standards, e. g., ISO 4463-1 and ISO 4463-3. The methodology of setting-out is discussed with the ordering party and marked points are handed over by a protocol. The setting-out parameters are printed on the setting-out drawing, which is annexed to the setting-out protocol of the kiln base. Followingly, the position of rollers is being set out. The rollers’ position is in direct connection with the kiln longitudinal ax (Fig. 9.6). Their setting-out is done

Fig. 9.5  Control points for height measurement in the rotary kiln base

9.2  Geodetic Works Related to Rotary Kiln Assembly

185

Fig. 9.6  Scheme of steel plates and their position on the rotary kiln base

Fig. 9.7  Numeric and graphical visualization of rollers’ axes

by using the reference line, which is marked by holes on steel plates (of size about 100 mm × 200 mm and of a thickness of 2–3 mm). According to this, the plates should be fixed before (Fig. 9.7). The setting-out of the rollers is made in two steps: • Setting-out of the rollers’ ax in the lateral direction • Setting-out of distances between the rollers For setting-out works, only calibrated steel tape with acceptance of all necessary corrections can be used, eventually another method of appropriate accuracy. The required accuracy is given by limits uv for setting-out of: • • • •

The relative direction (orientation) of the neighborhood base blocks uv = 2 mm The distance up to 25 m – uv = 3 mm The distance up to 50 m – uv = 5 mm The distance larger than 25 m – uv = d. 1/10,000 (d is the distance setting-out in m)

For setting-out of heights, only the well-known leveling method is being used. During the leveling, we should use calibrated scales or leveling staffs with invar tape. The vertical position of rollers’ axes is given with relation in the definition triangle (Fig. 9.10) or according to the horizontal reference plane of the rotary kiln. The limit for setting-out of all heights is given by 1 mm.

186

9  Setting-Out and Control of Rotary Kilns

The setting-out works should be finished with notice in the construction journal (site diary), of which necessary annex is the setting-out protocol. The protocol includes usual values of setting-out, limits, and maximal and actual setting-out deviations and the manner of points’ marking on the construction site. For settingout of the rotary kiln’s basement the methods usually applied for setting-out of buildings or civil engineering structures are used. The accuracy of setting-out is evaluated according to setting-out deviations given by rotary kiln design (documentation) or by relevant standards. Generally, it is given the maximal construction deviations (limits), which could be used for calculation of maximal setting-out deviations (limits).

9.3  G  eodetic Methods of Rotary Kiln Control and Rectification The main role of control measurements is the detection of the fulfillment of basic conditions given for the rotary kiln. According to the results of control measurements, it is checked if the longitudinal ax of the kiln has the given inclination as well as if the kiln main ax includes the definition triangle cups. Simultaneously, we need to check whether the roller’s axes are parallel with the kiln longitudinal ax, except rollers installed on the same base as the thrust rollers. Axes of these rollers should be in a given convergence. Control measurements can be grouped in measurements for determination: of the 2D position of elements, heights (vertical position), and additional parameters and information. To the group of 2D measurements belongs: • Measurements for determination of the 2D position of the shell ax according to the reference line (plane) • Measurements for determination of the position of the rollers’ axes • Measurement of distances between rollers’ axes and the reference line (plane) • Measurement of distances along with the inclined longitudinal ax of the rotary kiln • Measurement of the position of thrust rollers To height determination belongs measurements for determination of: • Relative heights and vertical movement of points of the kiln basement • Relative heights and vertical movement of the edges of steel plates set up on base blocks • Relative heights and vertical movements of rollers For the realization of additional measurements, we use special equipment and mechanical measures and scales. To this group of measurements belongs: • Control of the diameter of rollers and thrust rollers • Measurement of rollers’ girth by wrapping • Measurement of roller diameter by calipers

9.3  Geodetic Methods of Rotary Kiln Control and Rectification

187

• Measurement of the mesh of the gearing drive and the pinion • Control of the allowance between rides and the shell Control measurements start with the determination of rollers’ position (Fig. 9.8). First, we determine the position of the roller ax using centric targets, which signalize the ax position with appropriate accuracy on both the upper (point 1) and the lower end (point 3) of the roller ax. Next is determined the position of the ride (its center) on the roller, through measurement of values u and q. The required accuracy of determination of the ax position on the target is 0.5 mm. The position of the definition triangle cusp (point A) is calculated using measured values. The control measurement continues with the determination of the roller shape (form) and its abrasion. The roller diameter is determined by wrapping. To describe the roller, we use a special equipment form, which enables the determination of the relative height of the horizontal tangential plane to the roller top (Fig.  9.9). The equipment consists of a tripod with a fine vertical movement of the mechanical linear and level. In the case of correct (nondeformed) form of the roller, the height is constant, not changed during the roller’s rotation. Using this method and equipment, we can determine the deviation in height (form) with allowance of uh = 0.1 mm. The roller’s diameter is measured using calipers in different positions (minimum in each quadrant) with the allowance of ur = 0.1 mm. Distances between rollers and the reference line are determined by tape measurement according to the scheme given in Fig. 9.6. All distances are determined by double measurement with the allowance of ud = 1.0 mm. The settlement or inclination of the kiln and roller basement is determined by leveling with the allowance of uh = 0.5 mm of the measured height difference. The fulfillment of conditions for the correct operation of the rotary kiln is checked in the profiles of rides. The shape of the definition triangles (determined in each profile) is important; it should be an isosceles triangle with the base (the line connecting the rollers’ axes) in the horizontal position. In the case of deviations from the given shape, we calculate rectification parameters (values) for both rollers.

Fig. 9.8  Determination of the roller ax and the definition (indicial) triangle cusp

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9  Setting-Out and Control of Rotary Kilns

Fig. 9.9  Determination of the roller’s shape (form)

Fig. 9.10  Shift and deformation of the definition triangle

By shifting the rollers along the horizontal line, we reach the right position of the definition triangle cups and that way their correct shape (Fig. 9.10). The rectification of the triangle position should be in line with the requirements given for the drive gear and the pinion. In case of necessary change in the position of the drive gear, the correct gear mesh should be ensured. This could be achieved by a small elevation of the drive gear ax over the ax of the drives. In that context, the height of the drive gear ax is limiting for rectification of the kiln longitudinal ax.

9.4  Calculation of Rectification Parameters The measurements described upon are done with an aim to determine the correct position of definition triangle cups. By such a process, the rotary kiln is rectified, i.e., the correct position of the kiln longitudinal ax is achieved in space. According

9.4  Calculation of Rectification Parameters

189

to extreme operation load and conditions, it is not possible to rectify the rotary kiln in one simple step. After the rectification values are calculated, these are usually discussed with the head technician of the kiln or with the head of the montage group or the general repair. The decision about the next processes and about how the kiln is being rectified is done after a consultation. It can be done step by step or completely at once (in one step). Results that are disposed of for the decision-makers are the inclination of rollers’ axes, the heights of points of contact of the rides and the rollers, the position of the kiln longitudinal ax in the profile of rides, and the draft rectification parameters (values). Determination of correct rectification values requires good knowledge and description of geometry relation between rollers and the rotary kiln shell. The mathematical model for the determination of actual and designed values of the rotary kiln geometry is based on relations visualized in Fig. 9.11. When the rotary kiln ax is in point O and the ax of the rollers in position O1 and O2, the rectilinearity of the kiln longitudinal ax is ensured by rectification of the rollers’ position, i.e., the position of points O1 and O2. Measured values are determined according to the kiln reference frame in the profile of each ride (Table 9.1). The actual position of the rotary kiln and rollers in each profile will be determined by measurement or calculation of values m, n1, n2 = n1 + d (Fig. 9.11). The

Fig. 9.11  Relation between measured and determined values (cross-section)

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9  Setting-Out and Control of Rotary Kilns

Table 9.1  Measuring values Measured geometrical parameters of the rotary kiln in mm In horizontal plane (XY) In vertical sections (YZ) No. X m R r1 r2 5 0 1253 1672 597 596 4 15,414 1255 1670 578 587 3 27,909 1249 1662 586 593 2 40,882 1255 1660 582 594 1 54,941 1248 1657 582 596

ΔH 13 10 0 3 10

H 18,395 18,965 19,455 19,952 20,781

d 2346.5 2279.5 2313.0 2307.0 2267.5

Legend: No. number of the profile (ride), X stationing of profiles, m deviations of the rides from the reference line, R radius (range) of the ride, r1 radius of the left roller, r2 radius of the right roller, H heights of rides, ΔH difference in height between the left and the right roller ax, d distance of roller axes

vertical relation of the kiln geometry is described by H, H1, and H2 which are the top of the kiln rides and heights of rollers’ axes (in lieu of height H1 and H2 is measured height difference ∆H = H2 – H1). The vector of rectification values VY and VZ is determined by

VY = Y − LY , where LY = m + R,

(9.1)



VZ = Z − L Z , where L Z = H − R,

(9.2)

where Y and Z are vectors of horizontal and vertical coordinates of points of the kiln longitudinal ax. R is the vector which includes diameters of rides. m is the vector which includes distances between the rides and the reference line. H is the vector that includes the heights of the shell top In case of positive rectification values, the kiln ax moved to the right and up; in case of negative rectification values the ax moved left- and downward. If each measured point is determined by stationing, i.e., by coordinate Xi, coordinates of the rotary kiln center points will be given by Y = α Y − β L n , where α = 1 − β, β =

Z = α Z − β Zn .

X , Zn

(9.3) (9.4)

The rectification parameters of the kiln ax will be

VY = α Y − β Yn − LY ,

(9.5)

9.4  Calculation of Rectification Parameters

191

VZ = α Z − β Z n − L Z .



(9.6)

The rectification values of rollers (left “1”, right “2”) are determined:

(

)



(

)



(

)



(

)



vY 1 = VY − e ′1 − e 1 ,



vY 2 = VY − e ′2 − e 2 ,



v Z 1 = VZ − h1 − h′1 ,



v Z 2 = VZ − h 2 − h′2 ,



(9.7) (9.8) (9.9) (9.10)

where e1, e ′1 , e2, and e ′2 are projections into the horizontal plane of the actual and the designed values of R + r1. resp. R + r2. r is the vector of rollers’ diameters. The angles ω1 and ω2 of the definition triangles and the angle ε which describes the height difference between the rollers in each profile will be calculated by dd T + ( R + r1 ) ( R + r1 ) − ( R + r2 ) ( R + r2 ) T

ω1 = arccos

2d ( R + r1 ) ( R + r1 )

T

dd T + ( R + r2 ) ( R + r2 ) − ( R + r1 ) ( R + r1 )



2d ( R + r2 ) ( R + r2 ) ε = arcsin

∆H . d

,

(9.11)

T

ω2 = arccos

T

T

T

,

(9.12) (9.13)

Horizontal and vertical distances between the kiln ax and the axes of rollers will be calculated using equations:

e 1 = ( R + r1 ) cos ( ω1 + ε ) ,





e 2 = ( R + r2 ) cos ( ω2 + ε ) ,





h1 = ( R + r1 ) sin ( ω1 + ε ) ,





h 2 = ( R + r2 ) sin ( ω2 + ε ) ,



(9.14) (9.15) (9.16) (9.17)

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9  Setting-Out and Control of Rotary Kilns



e 1′ = ( R + r1 ) sin 30 = ( h1 − VZ1 ) tg30 VZ1 = h1 + VZ − h1′ h1′ = ( R + r1 ) cos 30 ,



e = ( R + r2 ) sin 30 = ( h 2 − VZ2 ) tg30 VZ2 = h 2 + VZ − h′2 h′2 = ( R + r2 ) cos 30 , ′ 2



(9.18)



(9.19)

In case the mesh is between the roller and the ride, values will be determined by the actual position of the kiln ax calculated using (R + r + t). The calculated distances (values) are checked by



e 1 = ( m + R1 ) − n1 e 2 = ( n1 + d ) − ( m + R ) ,



h1 = ( H − R ) − H 1 h2 = ( H − R ) − H2 .

(9.20) (9.21)



With substitution to relations (9.7), (9.8), (9.9) and (9.10), we receive the full determination (description) of the rectification values for rollers

(

)

(

vY 1 = VY − e ′1 − e 1 = α Y + β Yn − LY − e ′1 − e 1

(

)

′ 1

)

= α Y + β Yn − LY − h − VZ tg30 + e 1 

= α Y + β Yn − e 1 − αZ1 tg30 + β Z n tg30

(9.22)





(

vY 2 = α Y + β Yn − e 2 − αZ1 tg30 + β Z n tg30 + ( Z1 − h 2 ) tg30

)

+ ( Z1 − h1 ) tg30 − h1 + VZ − ( R + r1 ) cos 30 ,

(

(9.23)

)

− h 2 + VZ − ( R + r2 ) coos 30 tg30 , 









Applying the same equations, we can determine the rectification values vZ1 a vZ2. According to the requirements for economized rectification of the kiln, it is required to determine the optimal position of the kiln. In that case, the rectification values of points of the kiln longitudinal ax are determined by the algorithm for calculation of the minimum of the function

T W = tr ( VY − VZ ) ( VY − VZ )  = min.  

(9.24)

9.4  Calculation of Rectification Parameters

193

To solve this, we need to apply the LSM and substitute

( c = tr (αβ A = tr (α L C = tr (α L

a = tr αα T T



) ) T

1

Y

1

Z

T

(

b = tr ββ T

)

D = ab − c 2

) )

( ) = tr ( β L )

A2 = tr β LY T C2

(9.25)

T

Z

and the rectification values in the first and last profile (ride) will be determined by 1 1 ( bA1 − cA2 ) Yn = ( bA2 − cA1 ) D D 1 1 Z1 = ( bC1 − cC2 ) Z n = ( aC2 − cC1 ) D D Y1 =



(9.26)

The rectification values of the kiln ax in other profiles will be determined using Eqs. (9.3), (9.4), (9.5), (9.6), (9.7), (9.8), (9.9), (9.10), (9.11), (9.12), (9.13), (9.14), (9.15), (9.16), (9.17), (9.18) and (9.19). The final documentation of measurement and rectification of the rotary kiln includes the technical report, measured values, calculations, evaluation of the qual-

Fig. 9.12  Position of the rotary kiln ax and axes of rollers

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9  Setting-Out and Control of Rotary Kilns

ity with limits (allowance), and their fulfillment as well as visualization of all values. The graphic part of the final documentation includes graphs and drawings of: • Reference frame, situation, scheme of rides, and rollers • Position of the kiln longitudinal ax and the axes of rollers according to the reference line (Fig. 9.12) • Height of the kiln longitudinal ax and the axes of rollers • Measured and calculated values in each cross-section (profile), i.e., the definition triangle • Rectified position of the rollers • Deformation of the kiln longitudinal ax (Fig. 9.13) • Measured values of the shell ovality determination including diagrams (if these are required) (Fig. 9.14) • Overview of measured and calculated values in the form of tables

Fig. 9.13  Deformation of the rotary kiln longitudinal ax

Reference

195

Fig. 9.14  Deformation of the rotary kiln shape and circle diagrams in profiles of rides

Reference SMZ JELŠAVA. (2016). SMZ Jelšava. Prezentačné materiály [online]. Jelšava: SMZ. [cit. 2016.10.01] Dostupné na internete: http://www.smzjelsava.sk/sk/výroba

Chapter 10

Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities

Nuclear power plants are very complex installations with specific requirements mainly on the stability of the base (ground). The assessment of the locality and the regular control of objects of the power plant are needed. The chapter brings the description of the main power plant objects and their function and operation conditions. The methodology of all geodetic measurements applied during the power plant construction as well as operation is described including the data processing. At the end of the chapter information about the international audit and control over the operation of nuclear power plants is attached.

10.1  Motivation The fast economic growth of the last century was built on the use of fossil fuels – coal, gas, and oil, which lead to coverage of 85% of the energy consumption by these sources. In most of the lands around the world, the energy of rivers (hydropower) is used quite frequently, too. The motivation to find a new energy source started new and intensive development in the field of nuclear energy production. In the beginning, it had been based on thermal and fast reactors, later, on the base of thermonuclear reactors. Nuclear power and its production enable to save of the environment with the minimization of carbon emissions. Currently, there are more than 450 power reactors in the world with combined electrical capacity up to 400 GW. Intensive development in the field of nuclear energy production underlines the number of approximately 60 reactors, which are under construction and 150 reactors, of which construction is planned. In the United States, the discovery of the nuclear chain reaction by Fermi and Szilárd led to the creation of the first man-made reactor. The research reactor known as Chicago Pile-1 achieved criticality on December 2, 1942. Electricity was generated by a nuclear reactor on December 20, 1951, for the first time. It was at the EBR-I experimental station near Arco, in the US state, Idaho. The first reactor © Springer Nature Switzerland AG 2020 A. Kopáčik et al., Engineering Surveys for Industry, https://doi.org/10.1007/978-3-030-48309-8_10

197

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10  Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities

producing power for the power-grid was Obninsk, near Moscow, with the production of 5 MW electricity. The rapid development in this industry segment is documented by the number of power plants in operation, which was 350 in 1984, 439 in 2008, and more than 450 today. Half of these power plants operate in four countries  – in the United States (more than 100), in France (more than 60), in Japan (more than 50), and in Russia (more than 30). In 1957, the International Atomic Energy Agency (IAEA) had been established. Its main role is the promotion of peaceful use of nuclear energy and to inhibit its use for any military purpose, including nuclear weapons. According to information and documents published by IAEA, investment in nuclear research and the construction of nuclear power plants will be in the focus of advanced countries also in the future (IAEA 2019). Nuclear power plants are high-level demanding investments, which ensure excellent maintenance also from the surveyors’ side, before and during the construction as well as during the operation. It results from the requirements on the stability of their components (equipment and structures), which should keep their horizontal or vertical position during the whole life cycle. Disclosure in these relations or overlaying of tolerances (limit values) leads to critical situations during operation or to operation failures (Table 10.1). The effort to increase the safety and reliability of nuclear power plants leads to significant growth of costs – in the last 10 years had been noticed increase of all costs by 2.5 times per 1 kWh electricity production. The safety of nuclear power plants is monitored and guaranteed by national and international bodies and institutions (Fig. 10.1). Construction of large investments, with complex technical solutions to different kinds of nuclear power stations, requires more complex maintenance than any other kind of construction. The complex’s maintenance of the design, construction, and operation of nuclear power stations expects the integration of knowledge of different disciplines, within surveying, too. In the case of nuclear power plants, information and complex knowledge of methods that are used in the field of industry surveys, satellite geodesy, photogrammetry, statistic, prognostic, geophysics, geotechnics, etc. are required. The complexity of surveying tasks is notable mainly in case of measurements done in the industry environment and with required (often very high) accuracy. Specific conditions are completed by safety regulations and limits as well as the necessity to use personal protective aids and wearing. Table 10.1  Expectation of civil engineering structure failures No. 1 2 3 4 5 6 7

Structure Nuclear power plants Dams and reservoirs Bridges and lines (nets) Industry structures (halls, structures for technology, etc.) Civil engineering structures Buildings, houses, etc. Electricity lines, etc.

Current values of failure expectation 10−2 – 6·10−2 5·10−3 – 5·10−2 2·10−3 – 3·10−2 1·10−3 – 2·10−2 1·10−4 – 5·10−3 5·10−5 – 1·10−4 1·10−6 – 5·10−5

10.2  Assessment and Evaluation of the Locality for Nuclear Power Plant Construction

199

Fig. 10.1  Monitoring of safe operations of nuclear power plants (IAEA – International Atomic Energy Agency (www.iaea.org), WANO – World Association of Nuclear Operators (www.wano. info), US NRC – US Nuclear Regulatory Commission (www.nrc.gov))

10.2  A  ssessment and Evaluation of the Locality for Nuclear Power Plant Construction The selection of the locality for nuclear power plant (siting) construction is conditioned by more aspects. They can significantly affect costs, public acceptance, and safety of the installation. Siting is a multifaceted process involving many types of site characteristics. According to energy production, it is required to situate power plants near to large industrial and housing centers, which enables broad and efficient use of the produced energy. Another side says that large investments should be not situated in places with fertile land, agricultural production, as well as wooden or conservation areas. It should be taken into account that power plant operation is connected with big water consumption. When choosing the power plant locality, parallel with geological evaluation, which is done usually by governmental institutions, knowledge about the actual dynamic conditions of the Earth’s surface in the locality has to be used. Localities

200

10  Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities

with seismic activities or with large tectonic movements are not appropriate for power plant construction. The seismic activities significantly increase the costs of the power plant stability assurance, respectively make this impossible. Siting of the power plant on an active break (tectonic line) is unacceptable. All these aspects build requirements, which a priori enable or disable the possibility to evaluate the locality as appropriate for power plant construction. This kind of analysis and research create a base for the plan of localization of future power plants. In each locality, there are defined variants of plants’ localization, which helps to make a shortlist of construction sites possible to use in the future (Fig. 10.2). Based on this, a plan of power plant localization had been done. It is detailed research of the recent Earth’s movement or tectonic stability of the chosen localities. Parallel with long-term tectonic movement, the seismic characteristics of the locality, their sensitivity to seismic activities, as well as the nearby and remote earthquakes have to be surveyed. In this case, the evaluation (research) done by geodetic methods is closely connected with regional and local seismic research (Fig. 10.3). Time for evaluation of the locality is limited. Opposed to this, tectonic movements are slow (gradual), not in connection with human factors and activities, and the movement of measuring points is significant and noticeable only after a given time period. The limitation of evaluation, as well as research to a certain interval (time), requires an increase of measurement accuracy to such level, which enables registration of very small changes of tectonic movements. If it happens, results of the research are registered criteria, which disable the construction of the power plant in a chosen locality; in that case, the valuation (research) in a given area is stopped and new locality for power plant construction should be chosen. U.K. Netherland

Belgium

Poland

Germany Czech Republic Slovakia Austria

France

Switzerland

Slovenia

Hungary Romania Croatia Bosna & Hercegovina

Italy

Serbia Bulg

Mont. Maced.

Portugal Spain

Alb. Greece

Fig. 10.2  Localities evaluated for nuclear power plant construction in Europe

10.3  Main Objects of a Nuclear Power Plant

201

Fig. 10.3  Tectonic map of Slovakia

To reach the required reliability (authenticity) of results, it is important to start with the realization of geodetic measurements as soon as possible. It is required to have enough time between the time when the measurement started and the evaluation period. This leads to appropriate and operative planning of all research in the given locality, including geodetic measurements. Any measurements which are based on or use localization technics need a stable frame of relevant quality. Due to this, these measurements start with the creation of a geodetic frame (network) with appropriate configuration and quality. The nature of measurements made for research requires a higher quality of stabilization of geodetic points but in the consistency of their operative (in time) construction. Quality of the point stabilization should eliminate possible seasonal changes, changes due to soil humidity, changes due to underground water variations, slope movements, etc. in their position. The volume of geodetic works during the power plant preparation is significantly higher as it is in case of another kind of investment. That is the reason they are done with the participation of many surveying teams (companies). From this point of view, coordination of all surveying activities during the whole research is very important. Responsible for these is usually a licensed surveyor of the investor who manages the surveying activities not only during the valuation of the power plant locality but during their whole construction and operation, too.

10.3  Main Objects of a Nuclear Power Plant The nuclear power plant is a thermal plant, where the thermal energy necessary for electricity production is produced by a nuclear reactor. Thermal energy is distributed to a steam generator and is used for electricity production using a steam turbine

202

10  Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities

and a generator (Fig. 10.4). The main component of a nuclear power plant is the containment structure, with the reactor vessel inside, which includes control rods and fuel elements. The control (regulation) of the reactor operation is based on a movement of control rods. When control rods are inserted deeper into the reactor, the number of absorbed neutrons is higher, and the power generated by the reactor is smaller. Opposite, the extraction of the control rods leads to an increase in the power generated by the reactor (Fig. 10.5). The operation cycle of the reactor is between 10 and 12  months. During the operation break, part of the fuel is changed, and reactor general repair activities are performed. Also, equipment, which is a part of the power plant operation chain, is being checked. Steam generator is the heat exchanger between the primary and the secondary circuit, which generates steam used by the turbogenerator. The primary circuit includes systems for localization and elimination of accidents, equipment for reactor fuel change (including their operation and storage), manipulation of contaminated materials, and ventilation chimney including a special ventilation system. The secondary circuit ensures the change of the thermal and pressure energy produced by the steam generator to electricity. The second circuit includes mechanical equipment, which is the same as the equipment of classic thermal power plants. Each of the reactor blocks has two turbogenerators, which include the turbine, the generator, the actuator, and the generator of own consumption – all of them on the same ax (Fig. 10.6). Most of electric equipment and installation, regulation, and measurement systems are collected in the main machine hall. The power plant is operated by a control room, which includes equipment and systems for operation, regulation, measurement, as well as safety of the power plant. Information about the operation of the power plant is registered by the central information system. The power plant operation is supported by other services  – water management service, cooling service, diesel aggregate station, and wastewater station. Components of the primary and secondary circuits are situated in

Fig. 10.4  Pressurized water reactor scheme (Javys 2019)

10.4  Geodetic Measurements During Nuclear Power Plant Construction

203

Fig. 10.5  View into the reactor hall with the reactor casing (Javys 2019)

buildings (halls) connected to each other by the structure as well as by operation relations. The common and interactive location of these objects ensures a high demand for the accuracy of setting-out of these objects as well as their construction and long-term stability (Fig. 10.7).

10.4  G  eodetic Measurements During Nuclear Power Plant Construction Consequential to the tectonic evaluation of the appropriateness and stability of the given locality, the construction of the nuclear power plant is done. During the power plant construction, a broad spectrum of surveying methods and measurements is being applied, which belongs, mainly due to the accuracy requirements, to methods used in engineering surveying. These could be divided into groups: • • • • • • • •

Preparation works Creation of the geodetic frame (network) Overlaying the construction site Setting-out of the position of power plant objects Setting-out of components (structures, equipment, technology, etc.) Realization of control measurements Creation of the as-built documentation of the power plant Creation of documents for cadastre

204

10  Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities

Fig. 10.6  View on the generators (Javys 2019)

Fig. 10.7  Cross-section of the main machine and reactor hall

Up-to-date maps and information for the design should be ensured during the preparation period. All these works should be done in coordination with the investor and the designer to minimize duplicate production of maps and information as well as to ensure the required content and quality of these documents. For the realization of these measurements, the appropriate geodetic frame is being created, with adequate stabilization taking into account its usage for setting-out of the construction site as well as the production of documents for cadastre. In the case of small areas,

10.4  Geodetic Measurements During Nuclear Power Plant Construction

205

these could be used for setting-out works during the whole construction as well as the production of the as-built documentation of the power plant. The evidence of the ground use, the bonification of the ground, calculation of agricultural production loss, etc. are prepared from information given in maps created for the designer. According to this information decisions about the locality used for the power plant construction are taken. The list of property owners is being prepared, information about them is collected and drawings for cadastre are prepared, also. We may prepare also the exemption of the locality from agricultural and forest land sources from this information, too. Usually, geodetic measurements are done in a local geodetic frame (network). The use of the local frame makes the design and the setting-out of the power plant simpler. The geodetic frame of the power plant should be of the highest accuracy and long-term stability, but parallel to this, we should take into account also efficiency of the measurements, costs of the stabilization, and signalization of network points, as well as the maintenance of the network. Points included in the reference frame are stabilized usually by so-called deep stabilization using drilled wells filled by concrete (Fig. 10.8). The drill depth is given by geological conditions of the locality evaluated separately for each point. The drill head is equipped with a centration plate, which ensures the centration of instruments and targets with an accuracy of 0.2 mm. For measurement of heights, we use benchmarks installed on the drill shell 0.3 m above the terrain. During construction and later during the power plant operation, these measurements are repeated many times, usually with the same requirements to accuracy, as of their realization. Related to this, the application of optimization techniques is necessary.

Fig. 10.8  Deep stabilization of reference points

206

10  Design, Construction, and Operation of Nuclear Power Plants: Geodetic Activities

Information prepared for the cadastre and other governmental institutions should be produced in the valid national reference frame. Due to this requirement, the transformation between local and national reference frame should be established and used during the construction and the operation of the power plant. This should be accepted by all subjects, which participate in the power plant construction or provide service during the power plant operation. The stability of points is given by their situation (configuration) and the art of their construction. Configuration of the reference network follows the requirement of the continuous realization of all surveying works during the construction and operation, as well as the conditions described by the geologic research. The art of point stabilization should ensure first the centration of instruments and equipment with accuracy one rate higher as is the required accuracy for determination of their parameters and second their long-term stability. The first requirement is completed by a montage of centration plates on heads of all pillars. The second requirement is fulfilled by the appropriate choice of stabilization parameters (depth, diameter, the shape of the point construction). The network stability is regularly controlled by a series of measurements done by the methodology given by the first epoch (zero measurement). Setting-out of the power plant structures’ position should be done by the surveyor of the investor, which is in case of the nuclear power plants usually a governmental institution. The relation between structures and objects of the power plant is very important. Inconsistence in the position of objects leads to complications during the setting-out of technology equipment, which is in relation to each other. Setting-out of structure elements is made by the surveyor of the constructor. In the case of important structures, the control measurement is done by the investor’s surveyor. The highest attention is given to the main structures – the reactor hall, the machine hall with generators, and other equipment – which is in relation to the main structures. Special group of setting-out works builds the setting-out of inside components of the reactor casing and the construction of the shaft for the elimination of accidents, which is created by a double steel shell filled by concrete. Inside the shaft are stainless roof plates setting up on the set of consoles fixed by welding to the inside walls of the shell. The accuracy of the shell construction is given by: • Deviation of the realized inside shell structure in relation to the designed shape (dimension) is 5 mm, • Standard deviation of the setting-out of consoles 1 mm, • Limit value of the inside shell verticality is 2 mm per 30 m. According to these limits, the required accuracy of the setting-out works is 1 mm. Sufficient realization of all setting-out works related to the power plant construction, with the unusual construction, size, and art of montage, requires the implementation of the appropriate methodology, in many cases optimized to actual conditions and situations. The importance of nuclear power plant construction, as well as the effort to ensure maximal safety of its structures as an integrating factor significantly influencing all components of the complex power plant structure, is projected into

10.5  Geodetic Measurements During Nuclear Power Plant Operation

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surveying control measurements. Maximal attention is given to the main objects and structures of the power plant, mainly their stability in the vertical direction. For regular control of the stability of tenths of objects with thousands of measuring points during the operation, the precise leveling method is used, in connection with the hydrostatic leveling and the pendulum measurement. To control the settlement of power plant structures is important, due to the increasing load of the basement during construction and montage of the equipment. Consolidation of the ground (basement) during the construction is important due to the required stability of all power plant structures during their operation. The next group of control measurements done during the power plant construction is a set of measurements. The aim is to control the geometry and form of structures in points (parts), where equipment will be installed in the future  – crane runways, turbines, generators, pumps, complex of lines and pipes, etc. A separate set of control measurements creates the group of measurements used by the loading test of different equipment made before their set in operation. This kind of measurement is made during the fuel of tanks, lines, and pipes, before the start of different aggregates and during pressure tests. To this belongs the measurement, which is connected with the geometry (shape, form) check of the shaft used for localization of accidens. This test and control requires the application of a special methodology as well as the realization of all measurements at the highest accuracy level. The provider is given the preparation and completion of the as-built documentation of all structures of the power plant as well as all engineering lines at the construction site. The measurements are made continuously during the whole period of the plant’s construction, and parallel are prepared the original maps and drawings of these structures, usually in the scale M 1:500. The results of these measurements are used for the preparation of cadastral plans, which are made in cooperation with the power plant’s department for legal affairs.

10.5  G  eodetic Measurements During Nuclear Power Plant Operation The question of operation reliability and safety of industry structures is recently being discussed more and more often, especially of nuclear power plants. The general public demand for the overall increase of nuclear power plants’ safety leads to need of declaration of the stability of the plant’s structures, besides the measurement done. Also, measurements producing information about operation and impact in the structure surrounding are done. Increasing demand for the measurements is noticeable not only in the number and variability of measurements but also in their quality (accuracy). The reason for the higher demand for realization of control measurements is the fact that power plants are built in localities with the ground (soil) of lower quality

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(from the geological and hydrological conditions point of view), to protect agricultural and forest land, as well as the environment. During the power plant construction are made objects of unusually form and structure, or objects which include equipment installed on a separate (specially designed) basement. With the realization of these measurements, we receive information, which creates the base for: • Verification of the stability of power plant objects, structures, and technology complexes • Comparison of the actual and the assumed (theoretical) values of deformation • Verification of the construction quality • Prognosis of the development of deformations • Verification of the impact on the environment, load and operation to stability, reliability, and safety of objects The aim of comparison of the actual and theoretical values is the identification of differences between the design, calculation, and reality. Significant differences signalize errors in realized structures, or in the assumption, or in the realized measurement. Using measurement results and applying appropriate analysis, we could identify the imperfections and realize actions (steps) to correct these. Deformation measurements include control of the main power plant objects and structures (main machine hall, turbogenerators, and the reactor), cooling towers, objects with special operation, and equipment, where due to unfavorable geological conditions or operation load, the non-constant deformation is expected. All deformation measurements should be realized according to the design (project) of deformation measurements. In the case of measurement of structures (components, equipment), which belong to the same object and which are required the same set of measurements, the project of deformation measurements could be common. High attention should be given to the appropriate stabilization of control and measuring points, as well as the measuring equipment. A set of control points could be included in the local reference frame when these are appropriate according to their position, stability, and equipment. Measuring points are stabilized and signalized using classic marks of type, which enable the realization of measurements with a given methodology. Marks should be made from noncorrosive materials and should be prevented against their damage by coverage. Points are installed on different levels (floors) – according to the type of the object and the installed equipment (Fig. 10.9). To measure the deformation of nuclear power plant objects, we usually apply methods, which are generally used for deformation measurement of industry objects. It is important to take into account the high demand for accuracy of these measurements and special conditions in which these measurements are done. The most often used methods for realization of these measurements are: • • • •

Precise leveling Polar method Trigonometric method Alignment

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Fig. 10.9  Set of measuring points of the reactor hall (cross-section)

• Selected photogrammetry methods • Terrestrial laser scanning Special methods are used for continuous long-term measurement of deformations, which are made using permanently installed autonomous operated measuring systems based on: • Hydrostatic leveling • Pendulum observation Control measurements include objects of the main machine and the reactor hall, divided into the primary and the secondary circuit, as well as the objects inside the main hall. The set of control measurements realized inside the primary circuit include: • Vertical deformation of the reactor hall • Reactor inclination – using precise leveling, hydrostatic leveling, and pendulum measurement • Vertical deformation of turbogenerators and pumps • Determination of geometry parameters of the shaft for the elimination of accidents • Determination of geometry parameters of crane runways and cranes

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The set of control measurement of objects, which belong to the secondary circuit, include: • Vertical deformation of the main machine hall basement • Vertical deformation of turbogenerators – on the level of the lower base plate and pillars (−5.0 m), upper base plate, which held the installed technology on the level of +9.5 m and on the level of the technology (ca +10.5 m) • Geometry determination of crane runways and cranes The set of control measurements of objects outside the main halls include: • • • • • • •

Vertical deformation of cooling towers Vertical deformation and inclination of ventilation chimneys Vertical deformation of the diesel aggregate station Vertical deformation of the intermediate depot of the used reactor fuel Vertical deformation of supporting operation structures Vertical deformation of the pumping station and water tanks Determination of geometry parameters of crane runways and cranes

The time schedule of control measurement is determined by operation conditions and safety regulations of the power plant as well as geology and hydrology of the ground under structures. Control measurement of the reactor done by the hydrostatic leveling system and the pendulum is continuous. Measurements of objects of the primary and secondary circuits are done usually two times per year, one time during operation and one time during operation break. The geometry of the shaft of the elimination of accidents is realized during the construction and the pressure load test. The frequency of measurement of crane runways and cranes depends on the operation load as well as operational limits for the realization of these measurements. Parallel to these measurements, environmental (temperature, humidity, etc.) and operational conditions, which affect measurements, are registered, too. The registration of these data is made independently from the geodetic measurement (according to requirements of the operator or the providers of other measurements) usually with a period of 1 h, eventually 24 h. The actual value required for the time of geodetic measurements is calculated using the appropriate data for a data set. In special cases, environmental information can be registered in time, when the geodetic measurement is done. Usually, this includes: • • • •

Temperature of equipment, structures, measuring points, and the air Humidity of the air and the soil (ground) Level of the groundwater Monitoring of operation conditions (power, rpm, vibration, prolongation, relative deformation of components, etc.)

The importance of data processing of measurements done in nuclear power plants underlines mainly the question of their safety. According to the high demand for accuracy and reliability of results and their interpretation, it is necessary to take into account all factors, which significantly affect the results during the data

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processing. Based on experience and knowledge, it is necessary to pay special attention to data processing of the reference frame, mainly in cases when reference points are situated on objects or near the objects where deformation (deformation forces) could occur. The stability of the reference frame could be checked by the application of the congruent test of repeated measurements or other appropriate statistical test procedures. Also, the decision about the significance of deformation or changes in the position of measuring points should be made based on the results of appropriate statistical tests. Long series of these measurements enable the application of these tests at a higher level of reliability as it is usually in engineering surveying. On the other hand, high accuracy of measurements decreases the difference between the value of standard deviation and deformation, which builds higher demand for decision-making procedure (algorithm) applied to these measurement results. The essential component of data processing is a visualization of results. The actual development in this field enables the application of a large group of different algorithms and products existing on the market, using of which could generate a broad spectrum of visualization (animation) of the results. However, in many cases, the form and the content of the presentation (visualization) are results strictly defined by the order and follow the scheme of classical presentation used before (Figs. 10.10 and 10.11). From the safe operation of the power plant point of view, it is critical to know not only the current state (deformation) of the object but also its expected deformation. According to this, besides the usual data processing, it is required to provide information about the development in the future, too. Because of this reason, we create models, which describe the behavior of a power plant objects in the future, using information about the physical condition of the soil, the structure, the static and operation load, etc. The task of geodetic measurements (their results) is to verify these created models and in addition to help to increase the accuracy of the model parameters and that way the model’s reliability and credibility.

Fig. 10.10 Visualization of deformation of the lower and the upper base plate and the turbogenerator

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Fig. 10.11 Visualization of deformation of the reactor fastening

10.6  I nstitutions and Standards Supporting the Safe Operation of the Nuclear Power Plant The organization responsible for nuclear power plant operation is fully responsible also for its safety. To ensure safe, reliable, and economic operation of a nuclear power plant, this should undergo regular safety reviews and assessments of their essential structures, systems, and components. A nuclear power plant consists of a thousand components and equipment, as well as systems, which should be operating at the required level of reliability. The coordination and safe operation of all systems and power plant components are possible thanks to the central system – instrumentation and control (I&C) systems. These systems enable continuous monitoring of the present state of the power plant, to identify potential problems and help the power plant personnel to understand and answer these. The International Atomic Energy Agency (IAEA) is the world’s center for cooperation in the nuclear field and seeks to promote the safe, secure, and peaceful use of nuclear technologies. The fundamental principles, requirements, and recommendations of safe operation of a nuclear power plant are collected in the IAEA’s key publication  – IAEA Safety Standards. This consists of three sets of publications devoted to Fundamentals, Requirements, and Guides (IAEA 2019). According to the IAEA guidelines, it is essential to identify all requirements of the nuclear power plant for their overall life cycle and formulate these in the form of the plant life management (PLiM) program. The PLiM ensures that the power plant is able to integrate its operation, maintenance, engineering, regulation, and other activities in line with requirements of safe long-term operation.

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IAEA also supports regulatory bodies of member states with technical advisory and safety review services to enhance their capacity for independent, effective regulatory supervision of nuclear power safety in their country. IAEA also delivers training and offers any assistance and expert missions to member states and help member states also with technical reports and safety review service. According to this, IAEA offers an Independent Engineering Review of I&C Systems (IERICS), which includes a detailed technical assessment of I&C systems provided by the mission team. The mission team is created by international experts and IAEA staff. The Nuclear Operators’ Forum, initiated in 2011 as part of the implementation of the IAEA Action Plan on Nuclear Safety, is meant to enhance cooperation among nuclear owner/operating organizations in strengthening the safety and effectiveness of nuclear electricity generation. It offers a platform for senior leaders from the operating organizations and support institutions to identify and share experiences, approaches, and strategies influencing safety and performance excellence of nuclear facilities in the long term.

References IAEA. (2019). International Atomic Energy Agency. http://www.iaea.org/resources/safety-standards/search. Accessed 6 Dec 2019. JAVYS. (2019). Nuclear and Decommissioning Company, Slovakia. https://www.javys.sk/en/ popup/information-service/multimedia. Accessed 19 Dec 2019.