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Lambert Wanninger, Stephan Wallstab-Freitag

Combined Processing of GPS, GLONASS, and SBAS Code Phase and Carrier Phase Measurements. Lambert Wanninger, Stephan Wallstab-Freitag Geodetic Institute, Dresden University of Technology, Germany. ION GNSS 2007, Session D2.

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Lambert Wanninger, Stephan Wallstab-Freitag

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  1. Combined Processing of GPS, GLONASS, and SBAS Code Phase and Carrier Phase Measurements Lambert Wanninger, Stephan Wallstab-Freitag Geodetic Institute, Dresden University of Technology, Germany ION GNSS 2007, Session D2

  2. GPS+GLONASS+SBAS • Maxim: The more satellites the better. • but several differences: • reference systems (GLONASS)  transformation • orbit accuracy (GLONASS, SBAS)  weighting • observation quality (GLONASS, SBAS)  weighting • inter-channel biases (GLONASS)  algorithm, estimation

  3. Orbit Accuracy GPS/GLONASS Broadcast orbit accuracy (source: JPL, IGS) Precise IGS orbits GPS (final): <5 cm GLONASS: 15 cm

  4. Observation Quality GPS/GLONASS Code Observations: Elevation dependence of MP1 Station 1 / Receiver 1 Station 2 / Receiver 2 Proper weighting required  receiver dependence

  5. GPS+GLONASS+SBAS Observation Equations for Single-Difference Carrier Phases GLONASS inter-channel bias difference [cm]:

  6. GLONASS Inter-channel Bias Diff. Double-Difference Residuals L1 GPS GLONASS GLONASS GLONASS inter-channel biases removed

  7. GLONASS Inter-channel Bias Diff. Long-term Stability L0 – iono.-free linear combination

  8. GLONASS Inter-channel Bias Diff. • Temperature effects • Chilling: • 20° Celsius temperature difference • no effect but change of antenna affects inter-channel bias difference L0 – iono.-free linear combination

  9. GLONASS Inter-channel Bias Diff. A priori values of [cm]

  10. Baseline Results GPS/GLONASS RTK-like processing: short baseline, 2 minutes of observations

  11. SBAS • Code and carrier phase • observations to • GEO satellites • presently • 10 SBAS satellites, • 4 over Europe, • just single-frequency • EGNOS • presently: • poor broadcast orbits+clocks •  short baselines only

  12. Observation Quality GPS/SBAS Code observations: elevation dependence of MP1 dual-frequency GPS MP1 single-frequency GPS MP1´ single-frequency SBAS MP1´

  13. SBAS RTK-like processing: short baseline, 2 minutes of observations, dual-freq. GPS, single-freq. SBAS  single-frequency SBAS improves dual-frequency GPS

  14. SBAS Carrier Phase Multipath Double-difference residuals L1: short static baseline, 2 SBAS satellites daily multipath pattern, but also changes in pattern: due to daily repetition of orbits, orbit maneuvers

  15. Summary + Outlook • GLONASS • lower orbit accuracy • some receivers: lower accuracy of code observations • inter-channel biases • SBAS • presently + EGNOS only: very poor orbit accuracy • lower accuracy of code observations • single-frequency only • Bright future • GPS L5, dual-frequency SBAS • more GPS/GLONASS/SBAS satellites • Galileo / Compass / GLONASS CDMA • A bird in the hand is worth two in the bush.

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