Global Multi GNSS Processing at CODE

Transcription

1 GNSS Symposium, Berlin Global Multi GNSS Processing at CODE R. Dach, S. Schaer 1, M. Meindl, H. Bock, A. Jäggi, S. Lutz, L. Ostini, L. Prange, A. Steinbach, D. Thaller, P. Walser, G. Beutler Astronomical Institute, University of Bern 1Federal Office of Topography swisstopo

2 Global Multi GNSS Processing at CODE Outline 1. Introduction: What is CODE? 2. Introduction and comparison of GNSS 3. Orbit characteristics for the individual GNSS 4. Impact of adding GLONASS to GPS measurements for navigation purposes on global parameters 5. Summary and Outlook 2

3 The CODE analysis center CODE = Center for Orbit Determination in Europe joint venture between Astronomischen Institut der Universität Bern (AIUB) Bundesamt für Landestopographie swisstopo Bundesamt für Kartographie und Geodäsie (BKG) operationell since 1992, located at the University of Bern contributions to all product lines of the IGS from a rigorous multi-gnss processing (also contributing to the EPN and ILRS) all products are generated using the Bernese GPS Software developed and maintained by the AIUB 3

4 GNSS: Global Navigation Satellite System GPS: Global Positioning System GLONASS: Глобальная навигационная спутниковая система operated: U.S. department of Defence/Transportation military navigation system, open also to civil users reference: WGS-84, UTC(USNO) military navigation system, open also to civil users reference: PZ-90.02, UTC(SU) Galileo will be operated by a comercial company the first civil navigation system reference: GTRF, UTC(GST) Other GNSS In development/planning e.g., China (Compass/Beidou), Japan (QZSS) 4

5 Comparison of GNSS GPS GLONASS Galileo Number of satellites 32 (24) 15 (24) 0/2 (30) Orbital planes 6 (every 60 ) 3 (every 120 ) 3 (every 120 ) Satellites per orbital plane 4 (unequally) 8 (equally) 10 (equally) Orbital radius 26,560 km 25,510 km 30,000 km Inclination of orbital planes Revolution period ~ 11h 58m ~ 11h 16m ~ 13h 45m Ground track repeatability 1 sideral day 8 sideral days 10 sid. days Constellation repeatability ~ 23h 56m ~ 23h 56m ~ 23h 56m SLR reflectors two satellites all satellites all satellites Signal separation techn. CDMA FDMA CDMA Reference for orbits WGS-84 PZ GTRF Reference for system time UTC(USNO) UTC(SU) UTC(GST) 5

6 Comparison of currently active GNSS CODE provides orbits for all active GNSS satellites in the final, rapid, ultra-rapid product lines of the IGS: includes also unhealthy satellites (even during repositioning events) GLONASS orbit predictions are available for RT/NRT applications s tatus: October 2008 (day of year 2008:275) 6

7 GPS/GLONASS Orbit Comparison Number of active GPS and GLONASS satellites 7

8 IGS multi GNSS network Location of the combined GPS/GLONASS receivers status: July May October (day (day of year of year 2003:182) 2008:140) 2008:275) 8

9 IGS multi GNSS network Number of the combined GPS/GLONASS receivers 9

10 GPS/GLONASS Orbit Comparison GLONASS satellite accuracy provided by CODE 10

11 GPS/GLONASS Orbit Characteristics Ground track for the GPS constellation Ground track for G06 all satellites for one ten days for ten days day of year 2008:060 to

12 GPS/GLONASS Orbit Characteristics Ground track for the GLONASS constellation Ground track for R04 R01 all satellites for to R08 one ten days for ten days day of year 2008:060 to

13 GPS/GLONASS Orbit Characteristics Elevation Azimuth Diagram Zimmerwald Algonquin (Lat: (Lat: ; ; Lon: Lon: ) 7 28 ) all G06 GPS satellite satellites R04 all GLONASS satellite satellites day of year 2008:060 to

14 GPS/GLONASS Orbit Characteristics Number of stations tracking a GPS satellite Assuming the CODE final network with 5 cut off and 15 minutes sampling, day of year 2008:060 14

15 GPS/GLONASS Orbit Characteristics Number of stations tracking a GLONASS sat. Assuming the CODE final network with 5 cut off and 15 minutes sampling, day of year 2008:060 15

16 GPS/GLONASS Orbit Characteristics Number of observations per day and satellite Mean value after eight days Assuming the CODE final network with 5 cut off and 15 minutes sampling, day of year 2008:060 to

17 Comparisons of Global Solutions Repeatability of daily station coordinates RMS of 8 daily coordinate solutions CODE final solution for day of year 2007:060 to

18 PDOP: Constellation Effects Number of Satellites in View Example: Zimmerwald elevation cut off 5, day of year 2008:020 to

19 PDOP: Constellation Effects PDOP values for satellite constellation Example: Zimmerwald elevation cut off 5, day of year 2008:020 to

20 PDOP: Constellation Effects Spectra of PDOP values for sat. constellation Example: Zimmerwald elevation cut off 5, day of year 2008:020 to

21 Performance of a Kinematic Positioning CODE EPN network CODE EPN solution for day of year 2008:034 to

22 Performance of a Kinematic Positioning Results from a kinematic positioning Example: Zimmerwald (ZIM2) CODE EPN solution for day of year 2008:034 to

23 Performance of a Kinematic Positioning Allan deviation from a kinematic positioning Example: Zimmerwald (ZIM2) The Allan deviation reflects the noise behavior of a time series. It is comparable with the RMS of epoch differences. The time interval gives the length between these epochs. Up component CODE EPN solution for day of year 2008:034 to

24 Performance of a Kinematic Positioning Standard dev. for rapid static Positioning Example: Zimmerwald (ZIM2) The time series are divided into intervals for specific lengths. Within each of these intervals the standard deviation of the mean is computed and displayed. The length of the interval is varied. North component CODE EPN solution for day of year 2008:034 to 089 Up East component 24

25 Summary and Conclusions What did we learn from studying the orbit geometry? The GPS constellation has a strong repetition rate of a sideral day. is longitude dependent because each satellite follows its own ground track. has the dominant frequency at a sideral day in the spectrum of the variation of the satellite geometry. The GLONASS constellation has a higher variability (repetition rate of 8 sideral days after 17 revolutions). is independent from the longitude because of the shift in the ground track for each day. has the dominant frequency at once per revolution in the spectrum of the variation of the satellite geometry (uncertainty of the orbits?). 25

26 Summary and Conclusions Why to generate a multi GNSS solution? to reduce the impact of the strong GPS constellation frequency of one sideral day to the obtained products. to improve products with a high resolution in time (sqrt(n) law, robustness). to reduce the impact of multipath to the solution. to be in place for including the new GNSS (Galileo, Compass?) as soon as data are available. What can a multi GNSS solution never procide? to replace general improvements of the GNSS modelling (e.g., troposphere modelling). 26