Optics and optical instruments -- Field procedures for testing geodetic and surveying instruments

This document specifies field procedures for determining and evaluating the precision (repeatability) of terrestrial laser scanners and their ancillary equipment when used in building, civil engineering and surveying measurements. Primarily, these tests are intended to be field verifications of the suitability of a particular instrument for the immediate task at hand, and to satisfy the requirements of other standards. They are not proposed as tests for acceptance or performance evaluations that are more comprehensive in nature. This document can be thought of as one of the first steps in the process of evaluating the uncertainty of measurements (more specifically of measurands).

Optique et instruments d'optique -- Méthodes d'essai sur site des instruments géodésiques et d'observation

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INTERNATIONAL ISO
STANDARD 17123-9
First edition
2018-12
Optics and optical instruments —
Field procedures for testing geodetic
and surveying instruments —
Part 9:
Terrestrial laser scanners
Optique et instruments d'optique — Méthodes d'essai sur site des
instruments géodésiques et d'observation —
Partie 9: Scanners laser terrestres
Reference number
ISO 17123-9:2018(E)
ISO 2018
---------------------- Page: 1 ----------------------
ISO 17123-9:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: +41 22 749 01 11
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Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
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ISO 17123-9:2018(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and subscripts ................................................................................................................................................................................. 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Subscripts .................................................................................................................................................................................................... 3

5 Requirements and recommendations............................................................................................................................................ 3

6 Test principle ........................................................................................................................................................................................................... 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Procedure 1: Simplified test procedure ............................................................................................................................. 4

6.3 Procedure 2: Full test procedure ............................................................................................................................................. 4

7 Simplified test procedure ............................................................................................................................................................................ 5

7.1 Configuration of the test field..................................................................................................................................................... 5

7.2 Example 1: Target scan by full dome scan ....................................................................................................................... 7

7.3 Example 2: Two face target scan ............................................................................................................................................. 9

7.4 Measurements ......................................................................................................................................................................................... 9

7.5 Calculation .................................................................................................................................................................................................. 9

7.6 Derivation of a reference quantity for computing permitted deviations ..........................................12

7.6.1 Introduction ......................................................................................................................................................................12

7.6.2 Determination of measurement uncertainty of the target centers ...................................12

7.6.3 Derivation of the permitted deviation for the simple test procedure .............................13

7.7 Quantification of measurement deviations and judgement of the instrument for

the simple test procedure ...........................................................................................................................................................13

7.7.1 Analysis of distance measurements .............................................................................................................13

7.7.2 Remarks on the scale problem ..........................................................................................................................14

7.7.3 Analysis of further distance differences ...................................................................................................14

8 Full test procedure ..........................................................................................................................................................................................16

8.1 Configuration of the test field..................................................................................................................................................16

8.2 Measurements ......................................................................................................................................................................................17

8.3 Calculation ...............................................................................................................................................................................................18

8.4 Statistical tests .....................................................................................................................................................................................21

8.4.1 General description ....................................................................................................................................................21

8.4.2 Question a) .........................................................................................................................................................................22

8.4.3 Question b).........................................................................................................................................................................22

8.5 Derivation of a reference quantity for computing permitted deviation .............................................23

8.5.1 Determination of measurement uncertainty of the target centre ......................................23

8.5.2 Derivation of the permitted deviation for the full test procedure .....................................23

8.6 Quantification of measurement deviations and judgement of the instrument for

the full test procedure ...................................................................................................................................................................24

Annex A (informative) Example for the simplified test procedure ....................................................................................26

Annex B (informative) Example for the full test procedure ......................................................................................................28

Annex C (normative) Example for the calculation of an uncertainty budget of Type B ...............................36

Bibliography .............................................................................................................................................................................................................................43

© ISO 2018 – All rights reserved iii
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ISO 17123-9:2018(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee

SC 6, Geodetic and surveying instruments.
A list of all parts in the ISO 17123 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved
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ISO 17123-9:2018(E)
Introduction

This document specifies field procedures for adoption when determining and evaluating the uncertainty

of measurement results obtained by geodetic instruments and their ancillary equipment, when used in

building and surveying measuring tasks. Primarily, these tests are intended to be field verifications

of suitability of a particular instrument for the immediate task. They are not proposed as tests for

acceptance or performance evaluations that are more comprehensive in nature.

These field procedures have been developed specifically for in situ applications without the need for

special ancillary equipment and are purposely designed to minimize atmospheric influences.

The definition and concept of uncertainty as a quantitative attribute to the final result of measurement

was developed mainly in the last two decades, even though error analysis has already long been a part of

all measurement sciences. After several stages, the CIPM (Comité Internationale des Poids et Mesures)

referred the task of developing a detailed guide to ISO. Under the responsibility of the ISO Technical

Advisory Group on Metrology (TAG 4), and in conjunction with six worldwide metrology organizations,

a guidance document on the expression of measurement uncertainty was compiled with the objective

of providing rules for use within standardization, calibration, laboratory, accreditation and metrology

services. ISO/IEC Guide 98-3 was first published in 1995.

With the introduction of uncertainty in measurement in ISO 17123 (all parts), it is intended to finally

provide a uniform, quantitative expression of measurement uncertainty in geodetic metrology with the

aim of meeting the requirements of customers.

ISO 17123 (all parts) provides not only a means of evaluating the precision (experimental standard

deviation) of an instrument, but also a tool for defining an uncertainty budget, which allows for the

summation of all uncertainty components, whether they are random or systematic, to a representative

measure of accuracy, i.e. the combined standard uncertainty.

ISO 17123 (all parts) therefore provides, for defining for each instrument investigated by the procedures,

a proposal for additional, typical influence quantities, which can be expected during practical use. The

customer can estimate, for a specific application, the relevant standard uncertainty components in

order to derive and state the uncertainty of the measuring result.
© ISO 2018 – All rights reserved v
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INTERNATIONAL STANDARD ISO 17123-9:2018(E)
Optics and optical instruments — Field procedures for
testing geodetic and surveying instruments —
Part 9:
Terrestrial laser scanners
1 Scope

This document specifies field procedures for determining and evaluating the precision (repeatability)

of terrestrial laser scanners and their ancillary equipment when used in building, civil engineering and

surveying measurements. Primarily, these tests are intended to be field verifications of the suitability

of a particular instrument for the immediate task at hand, and to satisfy the requirements of other

standards. They are not proposed as tests for acceptance or performance evaluations that are more

comprehensive in nature.

This document can be thought of as one of the first steps in the process of evaluating the uncertainty of

measurements (more specifically of measurands).
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

me a s ur ement (GUM: 1995)

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and

associated terms (VIM)

ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in

probability

ISO 4463-1, Measurement methods for building — Setting-out and measurement — Part 1: Planning and

organization, measuring procedures, acceptance criteria

ISO 7077, Measuring methods for building — General principles and procedures for the verification of

dimensional compliance

ISO 7078, Building construction — Procedures for setting out, measurement and surveying — Vocabulary

and guidance notes

ISO 9849, Optics and optical instruments — Geodetic and surveying instruments — Vocabulary

ISO 17123-1, Optics and optical instruments — Field procedures for testing geodetic and surveying

instruments — Part 1: Theory
3 Terms and definitions

For the purpose of this document, the terms and definitions given in ISO 3534-1, ISO 4463-1, ISO 7077,

ISO 7078, ISO 9849, ISO 17123-1, ISO/IEC Guide 98-3 and ISO/IEC Guide 99 apply.
© ISO 2018 – All rights reserved 1
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ISO 17123-9:2018(E)

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Symbols and subscripts
4.1 Symbols
Symbol Quantity Unit
c sensitivity coefficient —
d calculated distance m and mm
calculated mean distance m and mm
d measured distance m
obs
Δ distance difference m and mm
e eccentricity mm
F F-distribution —
I turning axis error °
k coverage factor —
k zero point error m and mm
z zero point error m and mm
ν degree of freedom —
2 2
Ω sum of squared residual m and mm
θ tilting angle °
φ turning angle °
r residual calculated by means of m and mm
single distances
residuals calculated by means of the m and mm
mean distances
S instrument station —
experimental standard deviation for m and mm
s , s
a precision measure
experimental standard deviation for m and mm
an accuracy measure
σ theoretical standard deviation of a m and mm
population
T target point —
u uncertainty various
U expanded uncertainty with cover- various
age factor k
x, y, z Cartesian coordinate m
χ Chi-Square distribution —
ζ Index error of tilting axis °
ζ resolution mm
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ISO 17123-9:2018(E)
4.2 Subscripts
Subscript Term
c collimation axis error
cen centring of targets
d calculated distance
calculated mean distance
Δ difference
diff diffusion of the measuring beam
ec eccentricity of the collimation axis
I turning axis error
ia incident angle
i,j index for target
ISO-TLS of standard uncertainty of the TLS (type A)
k zero point error
m maximum
ms manufacture specification
m0 scale factor
n index for station
φ turning angle
p typical influence quantities for the TLS measurements
pr pressure
pri primary rotation axis
r measured range
rc roughness
rh relative humidity
S instrument station
se sighting axis deviation
sec secondary rotation axis
sta stability setup
T target point
temp temperature
θ tilting angle
v0 tumbling deviation
w set number or repetition number
xyz 3D point
x,y,z cartesian coordinate
ζv index of tilting axis
ζθ resolution tilting angle
ζφ resolution turning angle
5 Requirements and recommendations

Before commencing the measurements, the operator shall ensure that the precision in use of the

measuring equipment is appropriate for the intended measuring task.

The laser scanner and its ancillary equipment shall be in known and acceptable states of permanent

adjustment according to the methods specified in the manufacturer’s handbook.
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ISO 17123-9:2018(E)

The coordinates are considered as observables because of modern laser scanners they are the standard

output quantities. All coordinates shall be measured on the same day. The instrument need not, but

may be levelled.

Meteorological data shall be recorded during the data acquisition in order to derive atmospheric

corrections. If possible the option for meteorological corrections within the software of the laser

scanner should be used. If the systematic deviations, created by the non-consideration of the

atmospheric corrections are too significant, and the automatic correction is not possible, then the raw

distances shall be corrected manually.

The operator should note the actual weather conditions at the time of measurement and the type of

surface on which the measurements are made. The conditions chosen for the tests should match those

expected when the intended measuring task is actually carried out (see ISO 7077 and ISO 7078).

Tests performed in laboratories would provide results which are almost unaffected by atmospheric

influences, but the costs for such tests are very high, and therefore they are not practicable for most

users. In addition, laboratory tests yield precisions much higher than those that can be obtained under

field conditions.

This document describes one field procedure with two different amounts of work as given in Clauses 7

and 8. If enough time is available, the full test procedure according to Clause 8 is recommended. It

allows a more refined and reliable judgement of the instrument.
6 Test principle
6.1 General

As raw observation values of laser scanners the x-, y- and z-coordinates of single points are treated. In

contradiction to other geodetic instruments, for example total stations, these coordinates do not have

a representative geometrical meaning. Furthermore, single points cannot be reproduced by repetition.

The quality of the scans can only be derived from estimated geometrical elements, like planes, spheres

or cylinders.

In the proposed test procedures the targets and the software for the target centre detection, which are

both important parts of the standard laser scanner equipment, shall be used as key elements for the

evaluation of the achievable precision. The 3D distances between the targets serve as indicator for the

quality of the measurements. The distances are chosen as datum independent measures for levelled

and non-levelled instruments.

Other targets, like spheres, may be used instead of the standard targets, which are recommended by

the manufacturer.
6.2 Procedure 1: Simplified test procedure

The simplified test procedure provides an estimate as to whether the precision of a given laser scanner

equipment is within the specified permitted deviation in accordance with ISO 4463-1.

The simplified test procedure is based on a limited number of measurements. This test procedure relies

on measurements of x-, y- and z-coordinates in a test field without nominal values.

An accurate standard deviation cannot be obtained. If a more precise assessment of the laser scanner

under field conditions is required, the more rigorous full test procedure as given in Clause 8, should

be used.
6.3 Procedure 2: Full test procedure

The full test procedure shall be adopted to determine the best achievable measure of precision

and partly accuracy of a laser scanner and its ancillary equipment under field conditions within

an acceptable time. The geometry of the test field is identical to the geometry of the simplified test

4 © ISO 2018 – All rights reserved
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ISO 17123-9:2018(E)

procedure. In this test procedure three series of measurements are taken instead of one series as in the

simplified test procedure. In addition, the statistical tests are applicable only for this test procedure.

7 Simplified test procedure
7.1 Configuration of the test field

In total two instrument positions and four target marks, also called targets, are arranged in a horizontal

and a vertical triangle. The measurement setup is shown in Figure 1 and Figure 2. Both triangles share

one edge. The two instrument stations S and S as well as the two targets T and T are aligned on the

1 2 1 2

shared edge. This is necessary in particular for the determination of a systematic distance deviation.

The dimensions of the triangles and also the distance between the two instrument stations are

determined essentially by the range of the examined TLS and by the maximum distance for capturing

the targets as recommended by the manufacturer.

The following recommendations concerning the measurement setup shall be taken into account:

— The two instrument stations S and S as well as the two targets T and T shall be aligned on a line

1 2 1 2
in space.

— Both the horizontal and the vertical triangle shall be realized as right-angled triangles (each with a

right angle at target T ).

— The hypotenuse S T of the horizontal triangle shall match the maximum recommended distance

1 3

for target capturing. This distance will be called maximum distance d in the following.

— The distance T T of the vertical triangle should be made as long as the local conditions permit

2 4

and it shall however be at least one third of the maximum distance. Moreover, the target T shall

be observed in steep sighting. The minimum value of 27° for the tilting angle, under which T shall

be observed from S , is recommended (see Figure 2). Table 1 gives some examples for possible

configuration of the test field.

— The desirable ratio of the cathetus in the vertical triangle is 1:1. If possible, a ratio of 2:1 shall not be

exceeded, however only in case the site allows for placing T sufficiently high.
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ISO 17123-9:2018(E)
Key
S , S instrument station
1 2
T , T , T , T target point
1 2 3 4
d maximum distance
Figure 1 — Configuration of the test field
Key
S , S instrument station
1 2
T , T , T , T target point
1 2 3 4
d maximum distance
Figure 2 — Vertical plane of the test field
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ISO 17123-9:2018(E)

Table 1 — Examples of distances for the testfield-setup based on the maximum distance d

Elev.
a b c d e
|S T | |S T | |S T | |S T | |S T | Angle on
1 3 2 1 1 4 2 3 2 4
S to T
1 4
m m m m m
20,00 6,67 19,44 11,06 10,00 30,964
25,00 8,33 22,19 17,00 12,50 34,287
30,00 10,00 25,00 22,36 15,00 36,870
35,00 11,67 27,85 27,49 17,50 38,928
40,00 13,33 30,73 32,49 20,00 40,601
45,00 15,00 33,63 37,42 22,50 41,987
50,00 16,67 36,55 42,30 25,00 43,152
1/3 d
2 2
TT ++()55m+ ST m
24 21
2 2
d −+55m+ ST m
m 21
1/2 d

— Several laser scanners deflect the laser beam by rotations about two orthogonal axes, one slowly

rotating axis (primary rotation axis) and one fast rotating axis (secondary rotating axis). This type

of laser scanners typically can scan the complete surrounding by turning only by 180° about the

slowly rotating axis, while the fast rotating axis deflects the laser beam to the front side (face I) as

well as to the back (face II) of the laser scanner. In order to detect systematic deviations (e.g. axis

misalignments) of the laser scanner and reliably check the instrument the following orientation

rule is required.

On station S as well as on S the face in which T is scanned shall be different from the face in

1 2 3

which T and T are scanned. This means, in case the targets are scanned in a full-dome scan, the

2 4

“seam line” of the full-dome scan always shall run between T and T /T . On instrument station S

3 2 4 2

the targets T , T and T shall be scanned in a different face than on S (see Figure 3 and Figure 4

2 3 4 1
dark grey hemisphere and bright grey hemisphere of the dome).
7.2 Example 1: Target scan by full dome scan

The targets will be scanned by a single full-dome scan on each station. On instrument station S the

TLS instrument is oriented in a way that the first vertical scan line will run between T and T /T .

3 2 4

The targets T , T and T will be scanned in face I and T will be scanned in face II. On position S the

1 2 4 3 2

instrument will again be oriented in a way that the first vertical scan line will run between T and T /

3 2
T , but now T and T are scanned in face II, while T and T are scanned in face I.
4 2 4 1 3
© ISO 2018 – All rights reserved 7
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ISO 17123-9:2018(E)
Key
A face I
B face II
S , S instrument station
1 2
T , T , T , T target point
1 2 3 4
Figure 3 — Instrument orientations on both positions (side view)
Key
A face I
B face II
S , S instrument station
1 2
T , T , T , T target point
1 2 3 4
Figure 4 — Instrument orientation on both positions (top view)
8 © ISO 2018 – All rights reserved
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ISO 17123-9:2018(E)

The seam line of the full-dome scan needs to run between T and T /T . The faces on both instrument

3 2 4

positions shall be inverted but can also be vice versa. Dark grey colour indicates the face I and the

bright grey one the face II.
7.3 Example 2: Two face target scan

The TLS instrument offers target scanning functionality in both faces. If all targets will be scanned in

both faces a selection process shall be carried out. When evaluating the measurements on instrument

station S for T , T and T the target scans in face I will be considered, while for T the target scan in

1 1 2 4 3

face II shall be considered. When evaluating the measurements on S it shall be vice versa: For T and

2 2

T the target scans in face II shall be considered, while for T and T the target scan in face I shall be

4 1 3
considered.
7.4 Measurements

Before beginning the measurements the instrument shall become acclimatised to the ambient

temperature (if not stated else by the manufacturer in the user manual, use 2 min/°C difference for

acclimatization). All coordinates shall be measured within a 24 hour period.

After completing the measurements, point clouds of the targets in form of three-dimensional Cartesian

coordinates are available, from which the centre coordinates, e.g. of spheres or chessboard targets shall

be determined. For this work step, the corresponding processing sof
...

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