GNSS Signal Processing with Regional Augmentation Network

• US 20120293367A1
• Filed: 02/14/2011
• Published: 11/22/2012
• Est. Priority Date: 01/14/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Chen, Xiaoming, Vollath, Ulrich, Ferguson, Kendall
• Granted Patent: US 9,201,147 B2
• Time in Patent Office: Days
• US Class Current: 342/357.68
• CPC Class Codes: G01S 1/00 Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith position fixing by co-ordinating a plurality of determinations of direction or position lines G01S5/00
• CPC Class Codes: G01S 19/02 Details of the space or ground control segments
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/073 involving a network of fixed stations
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

Methods and apparatus for processing of GNSS data derived from multi-frequency code and carrier observations are presented which make available correction data for use by a rover located within the region, the correction data comprising: the ionospheric delay over the region, the tropospheric delay over the region, the phase-leveled geometric correction per satellite, and the at least one code bias per satellite. In some embodiments the correction data includes an ionospheric phase bias per satellite. Methods and apparatus for determining a precise position of a rover located within a region are presented in which a GNSS receiver is operated to obtain multi-frequency code and carrier observations and correction data, to create rover corrections from the correction data, and to determine a precise rover position using the rover observations and the rover corrections. The correction data comprises at least one code bias per satellite, a fixed-nature MW bias per satellite and/or values from which a fixed-nature MW bias per satellite is derivable, and an ionospheric delay per satellite for each of multiple regional network stations and/or non-ionospheric corrections. Methods and apparatus for encoding and decoding the correction messages containing correction data are also presented, in which network messages include network elements related to substantially all stations of the network and cluster messages include cluster elements related to subsets of the network.

Claims

1. A method of processing GNSS data derived from observations at multiple stations, located within a region, of GNSS signals of multiple satellites over multiple epochs, wherein the GNSS signals have at least two carrier frequencies and the observations include code observations and carrier-phase observations, comprising:

a. obtaining at least one code bias per satellite;

b. obtaining an ionospheric delay over the region;

c. obtaining a tropospheric delay over the region;

d. obtaining a phase-leveled geometric correction per satellite; and

e. making available correction data for use by a rover located within the region, the correction data comprising;

the ionospheric delay over the region, the tropospheric delay over the region, the phase-leveled geometric correction per satellite, and the at least one code bias per satellite.

2. The method of claim 1, wherein obtaining at least one code bias per satellite comprises obtaining an estimated code bias per satellite from a global network processor.

3. The method of claim 1, wherein obtaining at least one code bias per satellite comprises operating a processor to estimate a code bias per satellite from GNSS observations of reference stations of a regional network.

4. The method of claim 3, wherein operating a processor to estimate a code bias comprises operating a processor to fix a set of ambiguities and to estimate at least one code bias per satellite which is consistent with integer carrier-phase ambiguities.

5. The method of claim 4, wherein the code bias comprises a MW bias which is consistent with integer carrier ambiguities.

6. The method of claim 4, wherein the set of ambiguities comprises at least one of:

(i) widelane ambiguities and (ii) L1 and L2 ambiguities, (iii) L2E and L2C ambiguities, and (iv) a combination of carrier-phase ambiguities from which widelane ambiguities can be determined.

7. The method of claim 1, wherein obtaining an ionospheric delay over the region comprises operating a processor to determine the ionospheric delay over the region from a model.

8. The method of claim 1, wherein obtaining an ionospheric delay over the region comprises operating a processor to estimate from the observations an ionospheric delay per station per satellite.

9. The method of claim 1, wherein obtaining an ionospheric delay over the region comprises operating a processor to estimate from the observations an ionospheric delay per station per satellite and an ionospheric phase bias per satellite.

10. The method of claim 1, wherein obtaining a tropospheric delay over the region comprises operating a processor to estimate from the observations a tropospheric delay per station.

11. The method of claim 10, wherein the tropospheric delay per station comprises a zenith total delay per station.

12. The method of claim 1, wherein obtaining a phase-leveled geometric correction per satellite comprises operating a processor to estimate a set of ambiguities for satellites observed by the stations.

13. The method of claim 1, wherein obtaining a phase-leveled geometric correction per satellite comprises operating a processor to estimate a geometric correction which preserves integer nature of carrier-phase ambiguities.

14. The method of claim 1, wherein the phase-leveled geometric correction includes an integer-cycle bias per satellite.

15. The method of claim 1, wherein the correction data comprises at least one of (i) an ionospheric delay per station per satellite, (ii) an ionospheric delay per station per satellite and an ionospheric phase bias per satellite, and (iii) a tropospheric delay per station.

16. The method of claim 1, wherein the phase-leveled geometric correction per satellite comprises a geometric correction term for each of three locations within the region from which a geometric correction at an arbitrary location within the region can be determined.

17. A computer program product comprising:

a non-transitory computer usable medium having computer readable instructions physically embodied therein, the computer readable instructions when executed by a processor enabling the processor to perform the method of claim 1.

18. (canceled)

19. Apparatus for processing GNSS data derived from observations at multiple stations, located within a region, of GNSS signals of multiple satellites over multiple epochs, wherein the GNSS signals have at least two carrier frequencies and the observations include code observations and carrier-phase observations, comprising:

a. at least one processor configured to obtain at least one code bias per satellite, an ionospheric delay over the region, a tropospheric delay over the region, and a phase-leveled geometric correction per satellite; and

b. a communication channel to make available correction data for use by a rover located within the region, the correction data comprising;

the ionospheric delay over the region, the tropospheric delay over the region, the phase-leveled geometric correction per satellite, and the at least one code bias per satellite.

20. The apparatus of claim 19, wherein the at least one processor obtains the at least one code bias per satellite from a global network processor.

21. The apparatus of claim 19, wherein the at least one processor is operative to estimate a code bias per satellite from GNSS observations of reference stations of a regional network.

22. The apparatus of claim 21, wherein the at least one processor is operative to fix a set of ambiguities and to estimate at least one code bias per satellite which is consistent with integer carrier-phase ambiguities.

23. The apparatus of claim 22, wherein the code bias comprises a MW bias which is consistent with integer carrier ambiguities.

24. The apparatus of claim 22, wherein the set of ambiguities comprises at least one of:

(i) widelane ambiguities and (ii) L1 and L2 ambiguities, (iii) L2E and L2C ambiguities, and (iv) a combination of carrier-phase ambiguities from which widelane ambiguities can be determined.

25. The apparatus of claim 19, wherein the at least one processor is operative to determine the ionospheric delay over the region from a model.

26. The apparatus of claim 19, wherein the at least one processor is operative to estimate from the observations an ionospheric delay per station per satellite.

27. The apparatus of claim 19, wherein the at least one processor is operative to estimate from the observations an ionospheric delay per station per satellite and an ionospheric phase bias per satellite.

28. The apparatus of claim 19, wherein the at least one processor is operative to estimate from the observations a tropospheric delay per station.

29. The apparatus of claim 28, wherein the tropospheric delay per station comprises a zenith total delay per station.

30. The apparatus of claim 19, wherein the at least one processor is operative to estimate a set of ambiguities for satellites observed by the stations.

31. The apparatus of claim 19, wherein the at least one processor is operative to estimate a geometric correction which preserves integer nature of carrier-phase ambiguities.

32. The apparatus of claim 19, wherein the phase-leveled geometric correction includes an integer-cycle bias per satellite.

33. The apparatus of claim 19, wherein the correction data comprises at least one of (i) an ionospheric delay per station per satellite, and (ii) a tropospheric delay per station.

34. The apparatus of claim 19, wherein the phase-leveled geometric correction per satellite comprises a geometric correction term for each of three locations within the region from which a geometric correction at an arbitrary location within the region can be determined.