1. M. Gende, C. Brunini Universidad Nacional de La Plata, Argentina. Improving Single Frequency Positioning Using SIRGAS Ionospheric Products

2. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 2 Outlook Goal and motivations Why in South America? Workflow Results for a test bed Conclusions

3. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 3 Goal Increase precise positioning accuracy for single frequency receivers.

4. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 4 Motivation A large part of the GNSS technology users in Latin American have access only to single frequency receivers. These receivers can not eliminate the ionospheric bias by combining signals.

5. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 5 Basic Facts The ionosphere delay is the main error factor in positioning. This delay can be mitigated with a differencing technique. The technique lose effectiveness as the baseline increases.

6. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 6 Context in South America Because of the size of the continent, the GNSS continuously operating reference stations (CORS) are usually more than 300 kilometers from each other. Under this condition the relative positioning method is less effective.

7. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 7

8. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 8 Our proposal Use the CORS network already installed in order to produce ionospheric corrections for single frequency receivers.

9. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 9 Methodology Determine the slant total electron content (STEC) from dual frequency CORS. Estimate STEC in the place the user is located. Correct the single frequency observations. Process the observations in a regular way.

10. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 10 1 st step: calculate STEC using LPIM Absolute STEC must be determined. Receiver calibration The estimation is done at the zero difference level We assume a thin shell model.

11. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 11 2 nd step: Estimate STEC Estimate STEC For each receiver – satellite observation For each epoch

12. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 12 3 rd step: Correct the observations We can correct measurements Corrected C/A and Corrected L1 We can generate new measurements Simulated P2 and Simulated L2 The user has a new RINEX file with less ionospheric bias

13. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 13 4 rd step: Conventional processing Positioning is performed using the software that the user usually uses. We have extended the CORS – user’s distance.

14. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 14 Evaluation In the position domain Code and phase Static and cinematic Comparison Single frequency solution Corrected solution Ion free solution

15. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 15 Test bed 10 days, 24 hours. Mid latitude. Non disturbed solar conditions. Distance between GPS receivers 200 to 300 Km.

16. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 16

17. Standalone positioning

18. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 18 Horizontalcoordinates Horizontal coordinates C/A code C/A code + corrections Ion-free Delta North (meters) Delta East (meters)

19. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 19 Vertical component P1 Simulated ion-free Ion-free Delta Up (meters) Local Time (hours)

20. Differential positioning using code

21. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 21 Horizontalcoordinates Horizontal coordinates C/A code C/A code + corrections Delta North (meters) Delta East (meters) C/A C/A + corrections

22. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 22 Vertical component C/A C/A corrected Delta Up (meters) Local Time (hours)

23. Differential positioning using carrier phase

24. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 24 Local Time (hours) Delta North (meters) Delta East (meters) C/A C/A + corrections C/A C/A + corrections Horizontalcoordinates Horizontal coordinates

25. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 25 Vertical component Local Time (hours) C/A C/A + corrections

26. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 26 Conclusions It is possible to: Mitigate the ionospheric effect on L1. Extend the separation between the user and a CORS station. When corrections are applied: The horizontal errors are reduced more than 40%. The vertical errors are reduced almost 60%. 95% of the time the corrected observations present errors below. 1 centimeter for the horizontal coordinates. 10 centimeters for the height.

27. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 27 Extended utility

28. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 28

29. 4 September 2009. Buenos Aires, Argentina. IAG Scientific Assembly: Geodesy For Planet Earth. 29