HEPOS A look at the Transformation Between the ETRF and the Greek Reference Geodetic System

1. HEPOSA look at the Transformation Between the ETRF and the Greek Reference Geodetic System INF -2357 Vaios Balis – Christos Liapakis Geotech Ltd

2. Projects’ identification • Supervising authority: KTIMATOLOGIO SA “… responsible for the design, implementation and operation of the Greek Cadastral” • Projects: • HEPOS-SUPPLY • HEPOS-MEAS • Projects co-financed by the European Union under the operational programme “Information society”

3. HEPOS SUPPLY • “Supply, installation and maintenance of the fully operational and turnkey HEllenic POsitioning System – HEPOS” • Contractor: Trimble Europe B.V. • Sub-contractors • Geotech Ltd • Site Location • Installation • Operation support • OTENET SA • Communication provider

4. HEPOS SUPPLY • Reference stations: 100 (± 5) • Duration of the project: 2 years • Installation : 7 months • Site location • Reference station installation • Control center installation • Communications

5. HEPOS SUPPLY

6. HEPOS SUPPLY • 98 stations • 2 networks • 11 single RS • ETRF-2005

7. GGRS 87 • Greek Geodetic Reference System 1987 • Parallel to WGS 84 • Accuracy ~ 1 x 10-5 • Origin offset from WGS • +199.723 m • -74.030 m • -246.018 m • Projection • Transverse Mercator • Central Meridian: 24º • Scale along central Meridian: 0.9996

8. HEPOS MEAS – Scope of the work • “GPS measurements on control points of the Greek National Triangulation Network and calculation of their coordinates in HEPOS reference system (ETRF 2005, epoch 2007.5)” • “Calculation of 7-parameter transformation from HEPOS reference system to GGRS 87 and vice versa” • Contractor: JV Ceotech – Topomet • Duration : 10 months !!!!

9. Points to be measured • How many points per 1:50000 scale map sheet ? 1:50000 scale map sheet ~ 28 km ~ 22 km

10. 1:50000 scale map sheets • How many 1:50000 map sheets ?

11. Total number of points • How many points ? • 8 per each map sheet 1:50000 scale • 387 1: 50000 scale map sheets • or roughly 2800 points to be measured

12. Specifications • L1/L2 GPS receivers • Occupation time: 1 hour • Logging interval: 15 sec • Elevation mask : 15º • 6 satellites tracked : 90% of session time • PDOP < 4 : 75% of session time • 1 Primary base station – REF (24 hours logging) • 1 Secondary base station – SEC (logging until all 8 points of the map sheet have been measured)

13. GPS measurements

14. Resources • 10 survey crews • 2 people per survey crew • 5800 L1/L2 receivers with ACU • Handheld GPS for Guidance • Cameras for documentation • 4 WD for transportation • Daily data transfers to the office • 3 months field work • 9 months office work

15. Pre-survey office work

16. Some measured points

17. Some non measured points

18. Total measured points 2470 points

19. Measured point documentation

20. TGO projects 128 TGO projects

21. 7 parameter transformation • TTC SW

22. Transformation residuals

23. Transformation accuracy • 1:50000 scale map sheets • Horizontal • Mean value = ± 3 cm • Max Value = ± 5 cm • Vertical • Mean value = ± 6 cm • Max Value = ± 8 cm

24. Transformation accuracy • 1:100000 scale map sheets • Horizontal • Mean value = ± 6 cm • Max Value = ± 9 cm • Vertical • Mean value = ± 10 cm • Max Value = ± 17 cm

25. 7 parameter transformation (global) • TTC SW

26. Residuals

27. Residuals – North Greece

28. Residuals - Islands

29. Residuals – West Greece

30. Residuals – Central Creece

31. Residuals – North East Greece

32. Shift grid files

33. Shift grid files

34. Geoid

35. Accuracy

36. Survey controller application

38. Thank you for your attention…

39. Questions