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Compatibility of Receiver Types for GLONASS Widelane Ambiguity Resolution Simon Banville , Paul Collins and Fran çois Lahaye Geodetic Survey Division, Natural Resources Canada Presented at the PPP Workshop, 12-14 June 2013, Ottawa, Canada. Outline. GLONASS inter-frequency phase biases

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  1. Compatibility of Receiver Types forGLONASS Widelane Ambiguity ResolutionSimon Banville, Paul Collins and François LahayeGeodetic Survey Division, Natural Resources CanadaPresented at the PPP Workshop, 12-14 June 2013, Ottawa, Canada

  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. Inter-frequency phase biases Between-receiver phase observation • 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] Receiver-clock parameter Reference ambiguity DD ambiguity

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

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

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

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

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

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

  13. Inter-frequency code biases Javad Legacy [P1/P2] (7) Javad [C1/P2] (16) • 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. Inter-frequency code biases From NRCan Topcon NetG3 [P1/P2] (5+8) Topcon [C1/P2] (19) • Ionosphere-free IFCB (from PPP) Non-linear ??? “Outliers” Note: There is a certain consistency between models for Topcon receivers, although there are “outliers” and a dependency on antenna type.

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

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

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

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

  21. Application to Melbourne-Wübbena Internal consistency • Javad (14 stations) • 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. 78.7% < 0.15 cycles

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

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

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