1. Introduction to Micro-Triangulation
PACMAN meeting, CERN - Geneva, 26 May 2014
Vasileios VLACHAKIS

2. Outline Introduction to Micro-Triangulation Principle of triangulation
Historical triangulations
Precision at the level of microns
QDaedalus System
Hardware - Instrumentation
Software - Algorithms
Past results at CERN
Future developments
PACMAN meeting, CERN – Geneva, 26 May 2014

3. Principle of triangulation
Introduction to Micro-Triangulation Hz V
Zenith
Principle of triangulation
Measurements / Observations:
Distances (in order to fix the scale)
Directions (w.r.t. the horizontal plane)
Angles (as differences of directions)
Horizontal
Vertical or Zenith
Calculations / Estimations:
Distances (Unknown/Unmeasured)
Angles (Unknown/Unmeasured)
+ Coordinates w.r.t a reference system/frame
ATLAS Network measurements (LS1 - Feb 2014)
PACMAN meeting, CERN – Geneva, 26 May 2014

4. Principle of triangulation
Introduction to Micro-Triangulation
Principle of triangulation
As the Triangulation Network expands…
Incompatibility between Observations and Calculations!
Variation between repeated Observations!
PACMAN meeting, CERN – Geneva, 26 May 2014

5. Problem in Theoretical Model? OR / AND in Observations?
Introduction to Micro-Triangulation
Principle of triangulation
Incompatibility between Theory and Observations:
Closure residuals
a + b + c ≠ 180° or 200g or π
[degrees] [grads/gons] [rads]
c + d + e + f ≠ 360° or 400g or 2π
Variation between repetitive Observations:
Environment → better control
Instrumentation → more precise + accurate
Observer → better to avoid him! a b c d e f
Problem in Theoretical Model? OR / AND in Observations?
PACMAN meeting, CERN – Geneva, 26 May 2014

6. Principle of triangulation
Introduction to Micro-Triangulation
Principle of triangulation
Problem:
As the Triangulation Network expands…
…the errors propagate + accumulate!
PACMAN meeting, CERN – Geneva, 26 May 2014

7. Principle of triangulation
Introduction to Micro-Triangulation
Principle of triangulation
Solution:
Measurements:
Sufficient
Repeated
Redundant
Adjustment of observations:
Least Squares Adjustment
BLUE (Best Linear Unbiased Estimation)
PACMAN meeting, CERN – Geneva, 26 May 2014

8. Evolution of angle measuring instruments
Introduction to Micro-Triangulation
Evolution of angle measuring instruments
Dioptra
Heron of Alexandria (10-70 CE)
Theodolite
Jesse Ramsden ( )
Dimensions: 540x720x550 mm
Weight: 28kg
Accuracy: 20’’ - 60’’
Total Station
Leica Geosystems (1996)
Dimensions: 220x350x180 mm
Weight: 7.5kg
Accuracy: 0.5’’
PACMAN meeting, CERN – Geneva, 26 May 2014 8

9. Measuring the Meter! Introduction to Micro-Triangulation
Before the French Revolution, about 250,000 units of length and weight exist in France
Pierre François André Méchain ( ) and Jean Baptiste Joseph Delambre ( ) measured the meridian arc Dunkerque- Paris-Barcelona
This effort took place during the period from to 1799
“The meter" was defined as 1/10,000,000 of the distance North Pole - Equator.
The metric system was to be "pour tous pour toujours"
“Repeating circle” of Jean-Charles de Borda ( )
PACMAN meeting, CERN – Geneva, 26 May 2014 9

10. Measuring Earth's highest mountain
Introduction to Micro-Triangulation
Measuring Earth's highest mountain
Great Trigonometric Survey (19th century)
Colonel William Lambton established the mission in 1802
George Everest took leadership in 1823
Andrew Scott Waugh replaced Everest as Surveyor-General in 1843
Mount Everest was calculated (1852, published 1856) to be exactly 29000 ft /  m high
Current high ft / 8848 m
Error of 9.5 cm in a baseline of 11.6 km (≈ 8ppm)
PACMAN meeting, CERN – Geneva, 26 May 2014 10

11. Micro-triangulation Introduction to Micro-Triangulation
Principle of triangulation:
Measurements / Observations:
Distances (in order to fix the scale)
Directions (w.r.t. the horizontal plane)
Angles (as differences of directions)
Calculations / Estimations:
Distances (Unknown/Unmeasured)
Angles (Unknown/Unmeasured)
+Coordinates w.r.t a reference frame
Precision in level of micrometers:
Total Station precision ≈ g or 1.5 cc
Precision of 2.4μm/m
Precision at 4 m < 10 μm
dφ ≈ 1.5 cc
ds = R ∙ dφ
PACMAN meeting, CERN – Geneva, 26 May 2014

12. QDaedalus Introduction to Micro-Triangulation Measurement System:
Developed at ETH Zürich (Geodesy and Geodynamics Lab)
Performs contactless, automatic, high precision measurements
Originally developed for rapid and easy determination of astronomical φ, λ, Α
Successor of ICARUS
Low-cost, non-destructive upgrade for automated theodolites (or total stations)
Composed of both, hardware and software developments
PACMAN meeting, CERN – Geneva, 26 May 2014

13. The basic idea Introduction to Micro-Triangulation How it works?
The operator’s eye is replaced by a CCD camera
Non-destructive way
Easily and rapidly mount
A software reads out the image and the angles
Angle measurements obtained faster and more precise
What could be the precision?
Optical system resolution ≈ 4 arcsec/pixel
Object extraction ≈ 1/10 pixel or better
The achievable precision ≈ 0.4 arcsec (1.2 cc)
Total Station precision ≈ 0.5 arcsec (1.5 cc)
PACMAN meeting, CERN – Geneva, 26 May 2014

14. Components - Hardware Introduction to Micro-Triangulation
The complete system is composed by:
A Total Station / theodolite
TDA5005 by Leica Geosystems (1.5 cc)
A CCD camera
Guppy F-080C by Allied Vision Technologies (4.65 µm, 30 fps)
A steering device for the focus mechanism
P by Portescap
Interface box (CCD Triggering synchronization of multiple system)
A laptop with the software QDaedalus
PACMAN meeting, CERN – Geneva, 26 May 2014

15. Algorithms - Software Introduction to Micro-Triangulation
Optical target recognition (OTR) and measurement:
Center of mass
Template least-squares matching
Circle matching
Ellipse matching
Computer vision processing operations:
Image acquisition
Pre-processing (resampling, de-noising,…)
Feature extraction (lines, circles, regions,…)
Segmentation
High-level processing (compute center, size,...)
QDaedalus is developed in C++ on the open source development platform Qt
Qt allows fast creation of cross-platform programs with a graphical user interface
The image processing algorithms are based on the open-source library OpenCV
The management of the data is based on the database engine SQLite
PACMAN meeting, CERN – Geneva, 26 May 2014

16. Main features Introduction to Micro-Triangulation
Feature w.r.t. space/time resolution:
Density of points
Precision and Accuracy
Physical materialization of points
Sampling rate of measurements
Other important features have to be considered:
Automation degree
Palpate / touchless
Measurement range
Transportability
Easy handling
Price
PACMAN meeting, CERN – Geneva, 26 May 2014

17. CLIC module application
Introduction to Micro-Triangulation
CLIC module application
Automatic Micro-triangulation:
Import of approximate positions of station and targets
Definition of camera, focus, image processing parameters
Start of measurements, fully automatic process
Source: Sébastien Guillaume
PACMAN meeting, CERN – Geneva, 26 May 2014

18. Measurement of May 2012 Introduction to Micro-Triangulation Targets:
9 fixed and illuminated spheres of Ø8 mm
Comparison:
CMM with a precision of 6 μm MPE
After 3D Helmert transformation
Results:
1.5 cc, horizontal direction
1.5 cc, zenithal angles
PACMAN meeting, CERN – Geneva, 26 May 2014 18

19. Future developments Introduction to Micro-Triangulation Hardware
Instrumental precision is sufficient
Wireless transmission of data and image triggering capabilities
Size reduction would be welcome (easier mechanical adaptation of the camera to the telescope)
Higher acquisition (frame) rates, up to 50 Hz
Software
Synchronous steering of several total stations
Detection algorithm for an oscillating stretched wire and new fiducials
Targets
Develop and evaluate different types of fiducials, compatible with FSI
Method of marking points on the stretched wire
PACMAN meeting, CERN – Geneva, 26 May 2014 19

20. References Introduction to Micro-Triangulation
Bürki, B., Guillaume, S., Sorber, P., Oesch, H.-P. (2010). DAEDALUS: A versatile usable digital clip-on measuring system for Total Stations. International Conference on Indoor Positioning and Indoor Navigation (IPIN), Zürich, IEEE.
Griffet, S. (2010). Evaluation des performances du prototype de Micro-Triangulation. Survey report EDMS Document No , Genève, CERN.
Guillaume, S., Bürki, B., Griffet, S., Mainaud-Durand, H. (2012). QDaedalus : Augmentation of Total Stations by CCD Sensor for Automated Contactless High-Precision Metrology. FIG Working week 2012 Proceedings.
Schmid, M., Wanner, M., Manyoky, M. (2010). Suitability of the Daedalus System for Micro-triangulation. Geodetic Project Course, Geomatics Engineering and Planning.
Waniorek, S. (2011). Automatic Micro-triangulation. Survey report EDMS Document No , Genève, CERN.
PACMAN meeting, CERN – Geneva, 26 May 2014

21. Summary Introduction to Micro-Triangulation
Triangulation is a very old technique
Useful to obtain geometrical information
In short distances it is able to be precise at micrometer level
Changing the eye-piece with CCD we avoid the observer
Non-destructive upgrade of common Total Stations
Full exploitation of angle measurement precision at short distances (1-4 m)
The precision can be well predicted and it is completely depended on the configuration of the Micro-triangulation network
Developments needed in software, targets and hardware
PACMAN meeting, CERN – Geneva, 26 May 2014

22. Thank you! ?