ISO 17123-5:2005

INTERNATIONAL ISO
STANDARD 17123-5
First edition
2005-04-01

Optics and optical instruments — Field
procedures for testing geodetic and
surveying instruments —
Part 5:
Electronic tacheometers
Optique et instruments d'optique — Méthodes d'essai sur site des
instruments géodésiques et d'observation —
Partie 5: Tachéomètres électroniques




Reference number
ISO 17123-5:2005(E)
©
ISO 2005

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ISO 17123-5:2005(E)
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ISO 17123-5:2005(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 2
4 Requirements . 2
5 Test principle. 2
6 Simplified test procedure. 3
7 Full test procedure. 6
Annex A (informative) Example of the simplified test procedure. 12
Annex B (informative) Example of the full test procedure . 14

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ISO 17123-5:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 17123-5 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 6,
Geodetic and surveying instruments.
ISO 17123 consists of the following parts, under the general title Optics and optical instruments — Field
procedures for testing geodetic and surveying instruments:
— Part 1: Theory
— Part 2: Levels
— Part 3: Theodolites
— Part 4: Electro-optical distance meters (EDM instruments)
— Part 5: Electronic tacheometers
— Part 6: Rotating lasers
— Part 7: Optical plumbing instruments

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INTERNATIONAL STANDARD ISO 17123-5:2005(E)

Optics and optical instruments — Field procedures for testing
geodetic and surveying instruments —
Part 5:
Electronic tacheometers
1 Scope
This part of ISO 17123 specifies field procedures to be adopted when determining and evaluating the
precision (repeatability) of electronic tacheometers (total stations) and their ancillary equipment when used in
building 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 part of ISO 17123 can be thought of as one of the first steps in the process of evaluating the uncertainty
of measurements (more specifically of measurands). The uncertainty of a result of a measurement is
dependent on a number of factors. These include among others: repeatability, reproducibility (between-day
repeatability) and a thorough assessment of all possible error sources, as prescribed by the ISO Guide to the
expression of uncertainty in measurement (GUM).
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.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 3534-1, Statistics — Vocabulary and symbols — Part 1: Probability and general statistical terms
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
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ISO 17123-5:2005(E)
Guide to the expression of uncertainty in measurement (GUM), BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML,
1993, corrected and reprinted in 1995
International vocabulary of basic and general terms in metrology (VIM). BIPM, IEC, IFCC, ISO, IUPAC, IUPAP,
OIML, 2nd ed., 1993
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, the GUM and the VIM apply.
4 Requirements
Before commencing surveying, it is important that the operator ensure that the precision in use of the
measuring equipment is appropriate for the intended measuring task.
The electronic tacheometer and its ancillary equipment shall be in known and acceptable states of permanent
adjustment according to the methods specified in the manufacturer’s handbook, and used with tripods and
reflectors as recommended by the manufacturer.
The coordinates are considered as observables because on modern electronic tacheometers they are
selectable as output quantities.
The results of these tests are influenced by meteorological conditions, especially by the gradient of
temperature. An overcast sky and low wind speed guarantee the most favourable weather conditions. Actual
meteorological data shall be measured in order to derive atmospheric corrections, which shall be added to the
raw distances. The particular conditions to be taken into account may vary depending on where the tasks are
to be undertaken. These conditions shall include variations in air temperature, wind speed, cloud cover and
visibility. Note should also be taken of the actual weather conditions at the time of measurement and the type
of surface above 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 part of ISO 17123 describes two different field procedures as given in the Clauses 6 and 7. The operator
shall choose the procedure which is most relevant to the project's particular requirements.
5 Test principle
5.1 Procedure 1: Simplified test procedure
The simplified test procedure provides an estimate as to whether the precision of a given electronic
tacheometer 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. Due to the influence of
atmospheric refraction, the precision of the x- and y-coordinates is not equal to the precision of the
z-coordinates. Therefore the precision is calculated separately. The maximum difference is calculated as an
indicator for the precision.
A significant standard deviation cannot be obtained. If a more precise assessment of the electronic
tacheometer under field conditions is required, it is recommended to adopt the more rigorous full test
procedure as given in Clause 7.
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ISO 17123-5:2005(E)
5.2 Procedure 2: Full test procedure
The full test procedure shall be adopted to determine the best achievable measure of precision of an
electronic tacheometer and its ancillary equipment under field conditions.
This procedure is based on measurements of coordinates in a test field without nominal values. The
experimental standard deviation of the coordinate measurement of a single point is determined from least
squares adjustments.
When setting up the tacheometer for different series of measurements, special care shall be taken when
centring above the ground point. Achievable accuracies of centring expressed in terms of standard deviations
are the following:
 plumb bob: 1 mm to 2 mm (worse in windy weather);
 optical or laser plummet: u 1 mm (the adjustment shall be checked according to the manufacturer’s
handbook);
 centring rod: 1 mm.
Therefore it is recommended to use forced centring interchange for the test procedures
NOTE With targets at 100 m distance, a miscentring of 2 mm could affect the observed direction by up to 4″
(1,3 mgon). The shorter the distance, the greater the effect.
The full test procedure given in Clause 7 of this part of ISO 17123 is intended for determining the measure of
precision in use of a particular electronic tacheometer. This measure of precision in use is expressed in terms
of the experimental standard deviations of a coordinate measured once in both face positions of the
telescope:
s , s
iso XY iso Z
-TACH- -TACH-
Furthermore, this procedure may be used to determine
 the measure of precision in use of electronic tacheometers by a single survey team with a single
instrument and its ancillary equipment at a given time;
 the measure of precision in use of a single instrument over time;
 the measure of precision in use of each of several electronic tacheometers in order to enable a
comparison of their respective achievable precisions to be obtained under similar field conditions.
Statistical tests should be applied to determine whether the experimental standard deviations obtained belong
to the population of the instrumentation's theoretical standard deviations, σ, and whether two tested samples
belong to the same population.
6 Simplified test procedure
6.1 Configuration of the test field
Three instrument stations, S ( j = 1, 2, 3), shall be set out at the corner points of a triangle (see Figure 1). The
j
side lengths should be chosen according to the intended measuring task (e.g. 100 m to 200 m). The heights,
z , should be as different as the surface of the ground allows.
j
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ISO 17123-5:2005(E)

Figure 1 — Configuration of the test field
6.1.1 Measurement
Before commencing the measurements, the instrument shall be adjusted as specified by the manufacturer. All
coordinates shall be measured on the same day. The air temperature and the air pressure shall be measured
at each instrument station to derive the atmospheric corrections for distance measurements (input of the right
−6 −6
value to a factor of 10 ). The distances shall be corrected by a factor of 10 for any deviation of 1 °C in
temperature and/or for any deviation of 3 hPa (3 mbar) in air pressure. The correct zero-point correction
according to the reflector prism shall be used.
An arbitrary local coordinate system, (x, y, z), shall be established by assigning to the instrument station, S ,
1
the coordinates (e.g. 1 000, 2 000, 300). The zero-reading of the horizontal circle defines the x-axis.
From each instrument station, S ( j = 1, 2, 3), the coordinates of the other two points (target points) in the local
j
coordinates system shall be measured. The results of the measurements from instrument station S shall be
1
used as instrument station coordinates for S and S respectively for the subsequent measurements. Only one
2 3
backsight (to S ) shall be used for orientation.
1
On-board or stand-alone software shall be used for orientation. It is preferable to use the same software which
will be used for the practical work. All observations shall be made in one face position of the telescope.
Table 1 provides an observation scheme for the field measurements.
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ISO 17123-5:2005(E)
Table 1 — Observation scheme for the simplified test procedure
x-coordinate y-coordinate z-coordinate
(station-, running number) (station-, running number) (station-, running number)
Target point
m m m
Instrument station S Coordinates: (1 000, 2 000, 300) (take into account instrument and reflector height)
1
Orientation: arbitrary
S x y z
2 2,1 2,1 2,1
S x y z
3 3,1 3,1 3,1
Instrument station S Coordinates: (x , y z ) (take into account instrument and reflector height)
2 2,1 2,1 2,1
Orientation: backsight to S (1 000, 2 000, 300)
1
S x y z
3 3,2 3,2 3,2
S x y z
1 1,1 1,1 1,1
Instrument station S Coordinates: (x , y z ) (take into account instrument and reflector height)
3 3,1 3,1 3,1
Orientation: backsight to (1 000, 2 000, 300)
S x y z
1 1,2 1,2 1,2
S x y z
2 2,2 2,2 2,2
S is the instrument station or the target point j ( j = 1, 2, 3)
j
x is the kth measurement (k = 1, 2) of the x-coordinate of point j ( j = 1, 2, 3)
j,k
y is the kth measurement (k = 1, 2) of the y-coordinate of point j ( j = 1, 2, 3)
j,k
z is the kth measurement (k = 1, 2) of the z-coordinate of point j ( j = 1, 2, 3)
j,k

6.1.2 Calculation
The coordinate differences are calculated as follows:
dx=−x
11,1 1,2
dx=−x
22,1 2,2
dx=−x
33,1 3,2
dy=−y
41,1 1,2
dy=−y (1)
52,1 2,2
dy=−y
63,1 3,2
dz=−z
71,1 1,2
dz=−z
82,1 2,2
dz=−z
93,1 3,2
and the half difference of the maximum differences
1
dd= max (2)
x,yi
2 i=1, ., 6
and
1
dd= max (3)
zi
2 i=7, 8, 9
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ISO 17123-5:2005(E)
The half differences, d and d , shall be within the specified permitted deviation, ± p and ± p respectively,
x, y z x, y z
(in accordance with ISO 4463-1) for the intended measuring task. If ± p and ± p are not given, the half
x, y z
differences shall be d u 2,5 × s and d u 2,5 × s respectively, where s and
x, y ISO XY z ISO Z ISO XY
-TACH- -TACH- -TACH-
s are the experimental standard deviations of the x, y- and z-measurements respectively, determined
ISO Z
-TACH-
according to the full test procedure with the same instrument.
If the half differences, d and d respectively, are too large for the intended measuring task, it is necessary to
x, y z
make further investigations in order to identify the main sources of the deviations.
7 Full test procedure
7.1 Configuration of the test field
Three tripods, each having a forced centring device, S ( j = 1, 2, 3), shall be set out at the corner points of a
j
triangle (see Figure 1). The side lengths should be chosen according to the intended measuring task (e.g.
100 m to 200 m). The heights, z , should be as different as the surface of the ground allows.
j
7.2 Measurements
Before commencing the measurements, the instrument shall be adjusted as specified by the manufacturer. All
coordinates shall be measured on the same day. Forced centring interchange shall be used to eliminate
centring uncertainties.
Three series of measurements (m = 3, for i = 1,…, m) shall be carried out, each of which requires the
instrument to be put on one of the n = 3 tripods over point S (set j) of the test triangle in a fixed order, e.g.
j
S → S → S → S → S . The instrument should always be levelled carefully. No procedure of orientation for
1 2 3 1 2
the coordinate system of the instrument such as "free positioning with scale adaptation" shall be used. The air
temperature and pressure should be measured and the values used frequently to correct the electro-optic
distance measurements to insure that reliable atmospheric corrections are applied. The coordinates (x , y , z )
j j j
for each instrument setup shall always be set to zero (
...