Bernese GPS Software 4.2

Transcription

1 Bernese GPS Software 4.2 Introduction Signal Processing Geodetic Use Details of modules

2 Bernese GPS Software 4.2 Highest Accuracy GPS Surveys Research and Education Big Permanent GPS arrays Commercial users with Complex appl.

3 OVER VIEW Rapid processing permanent network processing ambiguity resolution Ionosphere Troposphere Antenna phase center calibrations simulation studies orbit determination earth rotation parameters free network solutions

4 General Features Code and phase data on both carriers linear combination of L 1 and L 2 single and dual frequency data baseline,campaign, multi-campaign Many parameters All receiver types(t) No numerical constants High degree automation menu driven

5 DATA FILES General Information Campaign Specific Information Program Specific Information

6 GPS Observables Range Pseudo Range Code pseudoranges Phase pseudoranges

7 Range biases Source Effect Satellite Orbital errors Clock biases Signal Propagation Tropospheric refraction Ionospheric refraction Receiver Antenna Phase Center Clock bias

8 Troposheric refraction Effect of the neutral part of earth s atmosphere Independent of frequency Effect is same for Code and phase measurements Systematic error

9 Ionospheric refraction Dispersive medium for microwave signals Frequency dependent and is propotional to Dealys code measurements 1 f 2 advances carrier phases Effect has same absolute value but the sign is opposite

10 Cycle Slips Obstruction of Satellite Signals Bad Ionosphere Condition Multi Path Satellite Elevation Receiver software failure Satellite oscillator malfunctioning

11 Ambiguity Initial Phase ambiguity Multiple Ambiguities

12 Linear Combinations (L 1 and L 2 ) Ionosphere free linear Combination L 3 L = 1 ( 2 2 f L - f ) L 2 2 f1 - f2 Ionosphere path delay is practically eliminated

13 Linear Combinations (L 1 and L 2 ) The Geometry free linear combination L 4 L = L - L Independent of receiver clocks and geometry Contains ionosphere delay and initial phase ambiguities Used for estimation of ionosphere models

14 Linear Combinations (L 1 and L 2 ) The Wide-Lane linear combination L 5 L = 1 ( f L - f ) L2 f1 - f2 Used at Double difference level for cycle slip fixing ambiguity resolution

15 Linear Combinations (L 1 and L 2 ) Melbourne-Wubbena linear combination L L = ± ( f L - f L )- ( f P f ) P2 f1 - f2 f1 ± f2 Eliminates effect of ionosphere geometry clocks troposphere

16 Transfer Rinex to Bern Format Code Zero differences Phase zero differences

17 Orbits Orbit type Quality(m) Availability Available at Broadcast 3.00 Real time Reciever Code predicted.20 Real time FTP Code Rapid.10 After 16hrs FTP Code Final.05 After 5 11 days FTP IGS Ultra rapid 0.20 After 3 hrs IGS IGS Rapid.10 After 14hrs IGS IGS Final.05 After 13 Days IGS

18 Errors in Baseline component due to orbit error Orbit error In m Baseline length Baseline Error in ppm Baseline Error in mm 2.5 m 2.5 m 2.5 m 2.5 m 0.5 m 0.5 m 0.5 m 0.5 m 1 km 10 km 100 km 1000 km 1 km 10 km 100 km 1000km.1 ppm.1 ppm.1 ppm.1 ppm ppm ppm ppm ppm - mm 1 mm 10 mm 100mm - mm - mm.2 mm 2 mm

19 CODSPP- Code single point positioning C/A code is sufficient Processes P-code if available Code Check for outliers Uses L 3 combination Receiver clock corrections Apriori coordinates

20 SNGDIF( Forming Baselines) Two stations and one satellite Both Code and Phase single differences Satellite Clock bias is cancelled Strategies Manual OBS-MAX Shortest

21 MAUPRP(manual and automatic pre processing) Only Phase measurements (A/S) Screens Single difference observations Checks double difference observations Two receivers and 2 satellites Receiver clock bias is cancelled Big jumps are marked Basic observables in bernese

22 Triple difference Solution Double differences over two epochs Triple diff.are used for pre-processing Phase ambiguities are eliminated Tropospheric refraction is reduced Ionospheric refraction and cycle slips stay Triple difference residuals Cycle Slip detection and repair

23 Cycle slip detection and Repair Corrects big jumps in single difference level Triple difference residuals are screened Strategies L 1, L 2, Both, Combined For L 1, L 2, Both No linear combination is taken

24 Cycle slip detection and Repair For Combined L3 combination is taken and screened for cycle slips All combinations are taken and the residuals are screened The observations are corrected for cycle slips If no good combination is found new ambiguity parameter is introduced If cycle slip is detected between two epochs the observations are marked

25 Parameter Estimation GPSEST Ambiguity free L 3 solution Ambiguity resolution for each baseline Final run for coordinate determination

26 Ambiguity free L 3 Solution Session Mode all observations To check quality of data Troposphere parameters Save residuals No final results

27 Ambiguity resolution For each baseline Strategies No Elimin Round Sigma Search QIF

28 Sigma dependant algorithm Every Linear combination baseline mode, session mode and several sessions Recommended: Only single frequency measurements with long sessions short baselines (less than 20km) for high quality code measurements with long sessions long baselines

29 Search Algorithm Suitable for Short baselines For single and both frequencies Short and Long sessions

30 QIF-Quasi ionosphere free For arbitrary baselines up to 2000km Long sessions L 3 combination all ambiguities are not resolved

31 Coordinate determination Session Mode All single difference files Ionosphere free L 3 combination No station is fixed Reference station coordinate is constrained Resolved ambiguities are introduced

32 Coordinate determination unresolved ambiguities are pre-eliminated Troposphere estimation is mandatory Coordinates and normal equation files for one session are stored

33 Coordinate determination The coordinates of multiple sessions are compared to obtain repeatibilities The normal equations for multiple sessions are used by ADDNEQ to give final coordinates