1. Compatibility of Receiver Types for GLONASS Widelane Ambiguity Resolution Simon Banville, Paul Collins and François Lahaye Geodetic Survey Division, Natural Resources Canada Presented at the PPP Workshop, 12-14 June 2013, Ottawa, Canada

2. 2 Outline  GLONASS inter-frequency phase biases  Calibration vs estimation of phase biases  Characterization of GLONASS inter-frequency code biases  Application to the Melbourne-Wübbena combination  Summary and future work

3. 3 Inter-frequency phase biases  Carrier-phase biases are only “apparent” biases:  Computing the reference ambiguity using [phase – code] can cause an apparent frequency-dependent bias due to a misalignment between phase and code observables. [Sleewaegen et al. 2012] Between-receiver phase observation Receiver-clock parameter DD ambiguity Reference ambiguity

4. 4 Inter-frequency phase biases From Sleewaegen et al. (2012).  Apparent carrier-phase biases:

5. 5 Calibration vs estimation  GLONASS inter-frequency phase biases can be calibrated [Wanninger 2012] :

6. 6 Calibration vs estimation  GLONASS inter-frequency phase biases can also be estimated on the fly [Banville et al. 2013] :  A system of n observations and n unknowns can be defined.  DD ambiguities will be integers if reference satellites have adjacent frequency numbers. Reference satellites

7. 7 Calibration vs estimation From Banville et al. (2013). UNBN (NovAtel) – UNBJ (Javad) baseline Ambiguities naturally converge to integers.

8. 8 Inter-frequency code biases  For long-baseline ambiguity resolution (or PPP), use of the Melbourne-Wübbena combination is often made.  Need to deal with inter-frequency code biases (IFCB)…  Application of the phase-bias estimation strategy can absorb the linear component of IFCB.  Do IFCB have a linear dependency on the frequency channel number?  If so: no calibration needed!  If not: are they consistent for a given receiver type?

9. 9 Inter-frequency code biases  Test network: 145 stations from EUREF on 2013-03-01

10. 10 Inter-frequency code biases  Pre-analysis using ionosphere-free code observations  Based on code residuals from PPP (GPS+GLONASS).  If ionosphere-free IFCB have a linear dependency on the frequency channel number, so will the narrowlane IFCB used in the Melbourne-Wübbena combination.

11. 11 Inter-frequency code biases Trimble [C1/P2] (32) Leica [C1/P2] (68)  Ionosphere-free IFCB (from PPP) Leica antennas without domes Ashtech antenna Older firmware Ashtech antenna

12. 12 Inter-frequency code biases NovAtel [C1/P2] (6) Septentrio [C1/P2] (4)  Ionosphere-free IFCB (from PPP) PolarX4 PolarX3 14 hours of data missing

13. 13 Inter-frequency code biases Javad [C1/P2] (16) Javad Legacy [P1/P2] (7)  Ionosphere-free IFCB (from PPP) AOAD/M_T OSOD Note: Javad Legacy receivers show a certain compatibility. Sampling was not sufficient to draw significant conclusions for other Javad models.

14. 14 Inter-frequency code biases Topcon [C1/P2] (19) Topcon NetG3 [P1/P2] (5+8)  Ionosphere-free IFCB (from PPP) ??? Note: There is a certain consistency between models for Topcon receivers, although there are “outliers” and a dependency on antenna type. From NRCan “Outliers” Non-linear

15. 15 Inter-frequency code biases  Summary  Most receivers show a quasi-linear dependency of the IFCB with respect to the frequency channel number.  For a given receiver make, IFCB can be affected by:  Antenna type and domes  Receiver model (and firmware version)  Residuals effects will propagate into clock/bias estimates and could create inconsistencies if not accounted for: calibration is required.

16. 16 Application to Melbourne-Wübbena  Methodology:  Estimate one set of daily satellite M-W biases (1/satellite) for Leica receivers.  Estimate one set of daily satellite M-W offsets (1/satellite) per receiver type (to check for receiver compatibility).  Estimate each station M-W bias, reference ambiguity and a widelane ambiguity per arc.  Fix ALL ambiguity parameters to closest integer and look at residuals.

17. 17 Application to Melbourne-Wübbena Internal consistency  Leica (68 stations) 92.8% < 0.15 cycles

18. 18 Application to Melbourne-Wübbena Internal consistency Offset w.r.t. Leica  Trimble (32 stations) 90.6% < 0.15 cycles

19. 19 Application to Melbourne-Wübbena Internal consistency Offset w.r.t. Leica  NovAtel (6 stations) 97.7% < 0.15 cycles

20. 20 Application to Melbourne-Wübbena Internal consistency Offset w.r.t. Leica  Septentrio (4 stations) 98.9% < 0.15 cycles

21. 21 Application to Melbourne-Wübbena Internal consistency  Javad (14 stations) 78.7% < 0.15 cycles Notes: Javad Legacy and Javad Delta don’t seem compatible. Javad Legacy only (7) [P1/P2]: 91.9% < 0.15 cycles Larger sampling needed to analyze Javad Delta.

22. 22 Application to Melbourne-Wübbena Internal consistency  Topcon (19 stations) 64.6% < 0.15 cycles Notes: Topcon NetG3, NetG3A, EGG_D and Odyssey don’t seem compatible. Dependency on antenna type and “outliers”.

23. 23 Summary and future work  Application of the phase-bias estimation strategy to the (undifferenced) Melbourne-Wübbena combination:  Removes the linear trend of the narrowlane IFCB.  Residual IFCB effects are estimated as a part of the M-W satellite biases.  One set (or more) of biases is needed per receiver type (unless compatible).  Not all receiver/antenna combinations can be accommodated by this approach at this point...  The method can still allow GLONASS widelane ambiguity resolution on a rather large subset of stations.

24. 24 Summary and future work  Future work  For ION GNSS 2013:  Apply M-W GLONASS biases to processing of long baselines.  What is the stability of GLONASS satellite M-W biases?  Generate ionosphere-free GLONASS satellite clocks.

25. 25 References  Banville, S., P. Collins and F. Lahaye (2013). “GLONASS ambiguity resolution of mixed receiver types without external calibration,” GPS Solutions. Published online.  Sleewaegen, J.M., A. Simsky, W. de Wilde, F. Boon and T. Willems (2012). “Demystifying GLONASS inter-frequency carrier phase biases,” InsideGNSS, Vol. 7, No. 3, pp. 57-61.  Wanninger, L. (2012). “Carrier-phase inter-frequency biases of GLONASS receivers,” Journal of Geodesy, Vol. 86, No. 2, pp. 139-148.

26. 26 Questions simon.banville@nrcan.gc.ca