new approaches in the use of laser trackers for ... · measurement (leica absolute tracker at402...

GSI Helmholtz Centre for Heavy Ion Research


New approaches in the use of laser trackers for

measurements of geodetic networks

Torsten Miertsch [email protected]

on behalf of the Survey & Alignment Team: I. Pschorn, V. Velonas, K. Knappmeier, A. Junge

[email protected]

mailto:[email protected]

mailto:[email protected]


“To be or not to be, that is the question” (from Shakespeare's “Hamlet”) "taH pagh taHbe'. DaH mu'tlheghvam vIqelnIS.“

Can the Leica AT402 be used as total station or not, that is the question

IWAA Grenoble 2016 2


Outline

Motivation of using the Leica AT402 as geodetic instrument an instrument which is directly related to the plumb line by its

own vertical axis and which is further mapping the earth surface

Comparison of evaluation methods

The polygon-versus-free-stationing scenario

Summary



Motivations

Objective Monitoring the eastern part of the existing GSI facilities for future FAIR

constructional activities by repeated 3D point network measurements


Area of investigation

existing facility new facility

FAIR GSI


Motivations

Sideline Comparison of evaluation

methods for the same network measurement (Leica Absolute Tracker AT402 tacheometer/total station vs. laser tracker plus level)

Can the Leica AT402 be used as centered instrument?

Comparison of measurement methods (polygon vs. free stationing)


U + = ?

vs.


AT402-free-stationing tacheometer versus laser tracker plus level observations

IWAA Grenoble 2016

The synchrotron as a geometrically circular machine (with a circumference of 217 m) was surveyed by the Leica AT402 (used in a levelled manner) and additionally levelled by the Leica DNA03

The investigation shows the influence on the coordinates, when the network is mathematically adjusted as a tacheometer network or as a laser tracker network plus levelling

laser tracker network without any correction to the earth curvature

laser tracker network corrected considering the earth curvature

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1. Case Evaluation as real laser tracker network plus additional levelling

2. Case The laser tracker considered as a tacheometer/total station and evaluated in this way



IWAA Grenoble 2016

The Leica AT402 treated as: Pure laser tracker plus additional levelling

Pure tacheometer/total station

• The Leica AT402 independent from its levelled orientation (three unknowns of orientation per station)

• The earth surface established by a net of height differences

• The levelled Leica AT402 considered as a tacheometer (one unknown of orientation per station)

• Corrections of zenith angle and slope distance by projections on the curved earth surface

Network adaptation locally to a sphere (R = 6371 km)

Establishment of the datum with 4 parameters (3 translations, 1 rotation around the

level axis)

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IWAA Grenoble 2016

Evaluation of both variants with the adjustment software PANDA

Both evaluations take the same datum definition (partial trace minimization/transformed adjustment)

Question show both evaluations the same values?

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IWAA Grenoble 2016

Topology of the deviation field in Z between tacheometer and laser tracker evaluation

-0.04

-0.05

-0.03

-0.05 +0.03

+0.03

+0.02

+0.06 ±0.00

-0.02

-0.02

-0.03

+0.07

+0.07

±0.00

-0.01 -0.04

-0.02

-0.01

+0.01

-0.01

-0.01

+0.02

-0.01

DZ [-0.05 , 0.07 mm]

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Transformation as tool of analysis tacheometer data set

(=DTa) data set attained by laser tracker plus level (=DLT)

horizontal deviations with no significant values (sd = 0.01 mm) the heights (Z-axis) showed distinctive features

Z-deviation in the graph DZ = DTa - DLT



IWAA Grenoble 2016

Evaluation as laser tracker plus levelling (blue disk)

Evaluation as tacheometer (deformed beige disk)

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The transformation of both data sets shows a flat disk being pushed through by a bent disk (in a topological meaning)



IWAA Grenoble 2016

Results Case 1 The Leica AT402 as pure laser tracker plus additional levelling

Case 2 The Leica AT402 as pure tacheometer

A posteriori standard deviations (1s) : • Azimuth = 0.15 mgon • Zenith = 0.15 mgon • Distance = 0.01 mm • Levelling = 0.4 mm/km

Small standard deviations in comparison to the

tacheometer evaluation not quite clear

Assumption 1. The free network adjustment of the laser tracker

(which itself shows the same deviation neighborhoods)

2. Then the projection to the earth surface

A posteriori standard deviations (1s) : • Azimuth = 0.20 mgon • Zenith = 0.30 mgon • Distance = 0.01 mm

Assumption larger standard deviation in the

zenith angle is an effect of pre-correction and the fixation of one orientation unknown about Z-axis

Deviation topology roughly periodic in the deviations (- + – + -)

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Polygon versus free stationing

First determination of the synchrotron point network with the methodology of free laser tracker stations

Second determination of the same point network with reciprocal observation stations in a polygonal / traverse net

Analysis of the centering accuracy of the Leica AT402



Polygon versus free stationing - The laser-tracker-centering -

Taylor-Hobson-centering (TH) with an adaptor from KERN to TH coming from the GSI TASA system

Standard tacheometer tribrach (with KERN-centering) as a connection tool to the adaptor

Determination of the trunnion/tilting axis height K via reciprocal observations

K

H1

H2

Column1

Column2

dz1 dz2

Z1

Z2

S2

S1 K



Polygon versus free stationing - The laser-tracker-centering -

Technique to determine the excentric error Measurement of surrounding points from the centered position Measurement of the same surrounding points plus the center point itself from a free station Transformation from the free-station-complex to the centered-point-complex

At the very beginning of the polygon measurement the excentric error was

determined figured in the sketch below First determined deviation between the directly measured point and its centered

situation in the synchrotron 0.15 mm the height difference corresponded to the trunnion/tilting axis height

Further independent examinations with other stations in the HEBT (high energy beam transfer) gave the following excentric error neighborhood 0.25 mm ± 0.15 mm


The Leica AT402 can be used as a centerable instrument, with an accuracy of the described values


Polygon versus free stationing - The network measurement and evaluation -

The synchrotron measured like an overlapped polygon

Every vertex/net point corresponds to a point on a dipole

Additional vertices by tripod stations to increase the geometric stability

IWAA Grenoble 2016

Shape nearly a dodecagon

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Polygon versus free stationing - Comparison -

IWAA Grenoble 2016

The A posteriori standard deviations of all measurement and evaluation variants

The free stationing cases

The polygon case Case 1 Laser tracker + level

Case 2 Tacheometer

Azimuth = 0.15 mgon Zenith = 0.15 mgon Distance = 0.01 mm

Azimuth = 0.20 mgon Zenith = 0.30 mgon Distance = 0.01 mm

Azimuth = 0.30 mgon Zenith = 0.30 mgon Distance = 0.20 mm An effect directly caused by

the excentric error

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Polygon versus free stationing - Results -

Transformation o polygonal network free stationing

network o Distortions close to 0.2 mm in their

coordinates

The deviations arose from the transformation correspond to the excentric error of the centered instrument itself (approx. 0.2 mm)


Deviation 3D-vectors of identical points regarding the transformation from the polygon to free stationing coordinates


Summary

Accelerator surveying “Accels” with an accuracy level at 0.1 up to 0.5 mm Land surveying “Fieldies” with an accuracy level at 0.5 up to 1.0 mm or larger

Question 1: Can the Leica AT402 be applied like a geodetic instrument? Answer for the “Accels”: Yes, for free stationing networks (accuracy level at 0.1 mm), for

standard procedures like blue lines, base networks (accuracy level at 0.5 mm) Answer for the “Fieldies”: Yes, for all tasks

Question 2: Can the observations of a levelled Leica AT402 be evaluated like tacheometer data? Answer for the “Accels”: Yes, but here some small effects occur regarding the zenith angle

(0.15 mgon up to 0.30 mgon) and therefore the height Z further investigations Answer for the “Fieldies”: Yes, without limitation. The levelling quality of Leica fulfils all

requirements

Question 3: Can the Leica AT402 be used as a centered instrument?

Answer for the “Accels”: In our case no, because the excentric error (approx. 0.25 mm) had a deteriorating effect and violated the accuracy level of 0.1 mm! further investigations

Answer for the “Fieldies”: Yes, the AT402 can be used in a centered manner



Summary

Question 4: Can the Leica AT402 be involved in polygon measurements with reciprocal observations? Answer for the “Accels”: In our case no, because the deteriorating excentric error (approx.

0.25 mm) influenced negatively on the polygon network adjustment (azimuth angle and much more the slope distance) and violated also the accuracy level of 0.1 mm! further investigations

Answer for the “Fieldies”: Yes, the AT402 can be used for polygonal lines / traverse lines

Question 5: Is there any increase in the geometric stability applying the

Leica AT402 in a polygonal way with reciprocal observations in comparison to the free-stationing-scenario? Answer for all: Not exactly! The excentric error can be traced back as a source of particular

influence (negative for accelerator measurement but negligible for the classical field surveys). But due to overlapping effects there is at the moment no chance to give a sufficient answer about the increase of the geometric stability!



Outlook

Open analyses: Combination of different laser trackers (especially from different

manufacturers) in identical networks

The involvement of new observation types direct slope distances between instruments in special combined networks (laser tracker ↔ laser tracker, laser tracker ↔ tachymeter, laser tracker ↔ theodolite)



Thank you for your attention!


French surveyors using a plumb level 1766 http://www.plumbbobcollectors.info/42014.html

new approaches in the use of laser trackers for ... · measurement (leica absolute tracker at402...

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