GNSS signal processing methods and apparatus with ionospheric filters

• US 8,558,736 B2
• Filed: 02/16/2010
• Issued: 10/15/2013
• Est. Priority Date: 02/22/2009
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Talbot, Nicholas Charles, Vollath, Ulrich
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/143,192
• Publication Number:
  US 20110279314A1
• Time in Patent Office: 1,337 Days
• Field of Search: 342/357.27
• US Class Current: 342/357.27
• CPC Class Codes: G01S 19/07 providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2

Abstract

Methods and apparatus are provided for processing a set of GNSS signal data derived from signals of a first set of satellites having at least three carriers and signals of a second set of satellites having two carriers. A geometry filter uses a geometry filter combination to obtain an array of geometry-filter ambiguity estimates for the geometry filter combination and associated statistical information. Ionosphere filters use a two-frequency ionospheric combination to obtain an array of ionosphere-filter ambiguity estimates for the two-frequency ionospheric combinations and associated statistical information. Each two-frequency ionospheric combination comprises a geometry-free two-frequency ionospheric residual carrier-phase combination of observations of a first frequency and observations of a second frequency. Auxiliary ionosphere filters use an auxiliary ionospheric combination to obtain an array of auxiliary-ionosphere-filter ambiguity estimates for the auxiliary ionospheric combinations and associated statistical information. Each auxiliary ionospheric combination uses carrier-phase observations of a third frequency and carrier-phase observations of at least one of the first frequency and the second frequency. A combined array of ambiguity estimates is prepared for all carrier phase observations and associated statistical information by combining the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters.

Claims

1. A method of processing a set of GNSS signal data derived from signals of a first set of satellites having at least three carriers and signals of a second set of satellites having two carriers, comprising:

a. applying to the set of GNSS signal data a geometry filter using a geometry filter combination to obtain an array of geometry-filter ambiguity estimates for the geometry filter combination and associated statistical information,

b. applying to the set of GNSS signal data a bank of ionosphere filters each using a two-frequency ionospheric combination to obtain an array of ionosphere-filter ambiguity estimates for the two frequency ionospheric combinations and associated statistial information, wherein each said two frequency ionospheric combination comprises a geometry-free two-frequency ionospheric residual carrier-phase combination of observations of a first frequency and observations of a second frequency;

c. applying to the set of GNSS signal data a bank of auxiliary ionosphere filters each using an auxiliary ionospheric combination to obtain an array of auxiliary-ionosphere-filter ambiguity estimates for the auxiliary ionospheric combinations and associated statistical information, wherein each said auxiliary ionospheric combination uses carrier-phase observations of a third frequency and carrier-phase observations of at least one of the first frequency and the second frequency, and

d. preparing a combined array of ambiguity estimates for all carrier phase observations and associated statistical information by combining the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters.

2. The method of claim 1, wherein the geometry filter combination comprises one of:

(1) a two-frequency geometry carrier-phase combination, (2) a single-frequency carrier-phase and code combination, and (3) a single-frequency carrier-phase and GRAPHIC combination.

3. The method of claim 2, wherein the two-frequency geometry carrier-phase combination is a minimum-error combination.

4. The method of claim 2, wherein the two-frequency geometry carrier--phase combination is a combination of the GPS L1 carrier frequency and the GPS L2 carrier frequency.

5. The method of claim 2, wherein the single-frequency carrier-phase and code combination is a combination of GPS L1 carrier-phase and GPS L1 code.

6. The method of claim 2, wherein the single-frequency of the single-frequency carrier-phase and GRAPHIC combination is the GPS L1 carrier frequency.

7. The method of claim 1, wherein the bank of ionosphere filters comprises one said ionosphere filter per satellite of the second set of satellites.

8. The method of claim 1, wherein the auxiliary ionospheric combination comprises one of:

(1) a two frequency geometry free ionospheric carrier-phase combination of the first frequency and the third frequency, and (2) a three frequency geometry-free ionospheric carrier-phase combination of the first frequency, the second frequency and the third frequency.

9. The method of claim 1, wherein the auxiliary ionospheric combination is a minimum-error combination.

10. The method of claim 1, wherein the bank of auxiliary ionosphere filters comprises one said auxiliary ionosphere filter per satellite of the first set of satellites.

11. The method of claim 1, further comprising applying to the set of GNSS signal data at least one code filter using a respective geometry-free code-carrier combination to obtain an array of ambiguity estimates for the code-carrier combinations and associated statistical information.

12. The method of claim 11, wherein preparing a combined array corn rises combining said arrays of said at least one code filter with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

13. The method of claim 11, wherein each geometry-free code-carrier combination comprises one of:

(1) a combination of a first-frequency code observation with a first and second-frequency carrier phase combination in which ionospheric bias of the first- and second-frequency carrier phase combination is matched to ionospheric bias of the first-frequency code observation; and

(2) a two-frequency narrow-lane code combination with a two-frequency wide-lane carrier-phase combination.

14. The method of claim 11, wherein said at least one code filter comprises one said code filter per satellite of the second set of satellites.

15. The method of claim 11, further comprising applying to the set of GNSS signal data derived from the first set of satellites at least one bank of additional filters, wherein each additional filter uses a geometry free and ionosphere-free carrier-phase combination of at least three frequencies to obtain an array of ambiguity estimates for the geometry free and ionosphere-free carrier-phase combination and associated statistical information, and wherein preparing a combined array comprises one of:

(1) combining said arrays of said additional filters with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information; and

(2) combining said arrays of said additional filters with the arrays of said at least one code filter and the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

16. The method of claim 15, wherein said at least one bank of additional filters comprises at least one said additional filter per satellite of the first set of satellites.

17. The method of claim 15 further comprising applying to the set of GNSS signal data at least one auxiliary code filter using a respective geometry-free auxiliary code-carrier combination to obtain an array of ambiguity estimates for the auxiliary code-carrier combination and associated statistical information, and wherein preparing a combined array comprises one of:

(1) combining said arrays of said additional filters with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information, (2) combining the arrays of said at least one auxiliary code filter with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters and the at least one code filter to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information, and (3) combining the arrays of said at least one auxiliary code filter with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters and the at least one code filter and the additional filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

18. The method of claim 17, wherein each auxiliary code-carrier combination comprises one of:

(1) a combination of a third-frequency code observation with a first-and third-frequency carrier phase combination in which ionospheric bias of the first-and third-frequency carrier phase combination is matched to ionospheric bias of the third-frequency code observation, (2) a combination of a second- and third-frequency code combination with a second- and third-frequency carrier phase combination in which ionospheric bias of the second- and third-frequency carrier phase combination is matched to ionospheric bias of the second- and third-frequency code combination, and (3) a combination of a three-frequency narrow-lane code combination with a three-frequency wide-lane carrier phase combination in which ionospheric bias of the three-frequency wide-lane carrier-phase combination is matched to ionospheric bias of the three-frequency code combination.

19. The method of claim 17, wherein said at least one auxiliary code filter comprises one said auxiliary code filter per satellite of the first set of satellites.

20. The method of claim 1, wherein the satellites are satellites of the Global Positioning System (GPS), wherein the first set of satellites have GPS carriers L1, L2 and L5 and wherein the second set of satellites have GPS carriers L1 and L2.

41. A non-transitory computer-usable medium having a computer readable program code embodied therein, said computer readable program code adapted to be executed to implement the method according to claim 1.

21. Apparatus for processing a set of GNSS signal data derived from signals of a first set of satellites having at least three carriers and signals of a second set of satellites having two carriers, comprising at least one processor with associated memory and a plurality of filters comprising:

a. a geometry filter using a geometry filter combination to Produce from the set of GNSS signal data an array of geometry-filter ambiguity estimates for the geometry filter combination and associated statistical information,

b. a bank of ionosphere filters each using a two-frequency ionospheric combination to obtain from the set of GNSS signal data an array of ionosphere-filter ambiguity estimates for the two frequency ionospheric combinations and associated statistical information, wherein each said two-frequency ionospheric combination comprises a geometry-free two-frequency ionospheric residual carrier-phase combination of observations of a first frequency and observations of a second frequency;

c. a bank of auxiliary ionosphere filters each using an auxiliary ionospheric combination to obtain from the set of GNSS signal data an array of auxiliary-ionosphere-filter ambiguity estimates for the auxiliary ionospheric combinations and associated statistical information, wherein each said auxiliary ionospheric combination uses carrier phase observations of a third frequency and carrier-phase observations of at least one of the first frequency and the second frequency, and

d. a combiner to prepare a combined array of ambiguity estimates for all carrier phase observations and associated statistical information by combining the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters.

22. The apparatus of claim 21, wherein the geometry filter combination comprises one of:

(1) a two-frequency geometry carrier-phase combination, (2) a single-frequency carrier-phase and code combination, and (3) a single-frequency carrier-phase and GRAPHIC combination.

23. The apparatus of claim 22, wherein the two-frequency geometry carrier-phase combination is a minimum-error combination.

24. The apparatus of claim 22, wherein the two-frequency geometry carrier-phase combination is a combination of the GPS L1 carrier frequency and the GPS L2 carrier frequency.

25. The apparatus of claim 22, wherein the single-frequency carrier-phase and code combination is a combination of GPS L1 carrier-phase and GPS L1 code.

26. The apparatus of claim 22, wherein the single-frequency of the single-frequency carrier-phase and GRAPHIC combination is the GPS L1 carrier frequency.

27. The apparatus of claim 21, wherein the bank of ionosphere filters comprises one said ionosphere filter per satellite of the second set of satellites.

28. The apparatus of claim 21, wherein the auxiliary ionospheric combination comprises one of:

(1) a two-frequency geometry-free ionospheric carrier-phase combination of the first frequency and the third frequency, and (2) a three-frequency geometry-free ionospheric carrier-phase combination of the first frequency, the second frequency and the third frequency.

29. The apparatus of claim 21, wherein the auxiliary ionospheric combination is a minimum-error combination.

30. The apparatus of claim 21, wherein the bank of auxiliary ionosphere filters comprises one said auxiliary ionosphere filter per satellite of the first set of satellites.

31. The apparatus of claim 21, further comprising means for applying to the set of GNSS signal data at least one code filter using a respective geometry-free code-carrier combination to obtain an array of ambiguity estimates for the code-carrier combinations and associated statistical information.

32. The apparatus of claim 31, wherein the combiner comprises means for combining said arrays of said at least one code filter with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

33. The apparatus of claim 31, wherein each geometry-free code-carrier combination comprises one of:

(1) a combination of a first-frequency code observation with a first- and second-frequency carrier phase combination in which ionospheric bias of the first- and second-frequency carrier phase combination is matched to ionospheric bias of the first-frequency code observation; and

(2) a two-frequency narrow-lane code combination with a two-frequency wide-lane carrier-phase combination.

34. The apparatus of claim 21, wherein said at least one code filter comprises one said code filter per satellite of the second set of satellites.

35. The apparatus of claim 31, further comprising means for applying to the set of GNSS signal data derived from the first set of satellites at least one bank of additional filters, wherein each additional filter uses a geometry-free and ionosphere-free carrier-phase combination of at least three frequencies to obtain an array of ambiguity estimates for the geometry-free and ionosphere-free carrier-phase combination and associated statistical information, and wherein the means for preparing a combined array comprises one of:

(1) means for combining said arrays of said additional filters with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information; and

means for combining said arrays of said additional filters with the arrays of said at least one code filter and the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

36. The apparatus of claim 35, wherein said at least one bank of additional filters comprises at least one said additional filter per satellite of the first set of satellites.

37. The apparatus of claim 35, further comprising means for applying to the set of GNSS signal data at least one auxiliary code filter using a respective geometry-free auxiliary code-carrier combination to obtain an array of ambiguity estimates for the auxiliary code-carrier combination and associated statistical information, and wherein the means for preparing a combined array comprises one of:

(1) means for combining said arrays of said additional filters with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information, (2) means for combining the arrays of said at least one auxiliary code filter with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters and the at least one code filter to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information, and (3) means for combining the arrays of said at least one auxiliary code filter with the arrays of the geometry filter and the ionosphere filters and the auxiliary ionosphere filters and the at least one code filter and the additional filters to obtain said combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

38. The apparatus of claim 37, wherein each auxiliary code-carrier combination comprises one of:

(1) a combination of a third-frequency code observation with a first-and third-frequency carrier phase combination in which ionospheric bias of the first-and third-frequency carrier phase combination is matched to ionospheric bias of the third-frequency code observation, (2) a combination of a second- and third-frequency code combination with a second- and third-frequency carrier phase combination in which ionospheric bias of the second- and third-frequency carrier phase combination is matched to ionospheric bias of the second- and third-frequency code combination, and (3) a combination of a three-frequency narrow-lane code combination with a three-frequency wide-lace carrier phase combination in which ionospheric bias of the three-frequency wide-lane carrier-phase combination is matched to ionospheric bias of the three-frequency code combination.

39. The apparatus of claim 37, wherein said at least one auxiliary code filter comprises one said auxiliary code filter per satellite of the first set of satellites.

40. The apparatus of claim 21, wherein the satellites are satellites of the Global Positioning System (GPS), wherein the first set of satellites have GPS carriers L1, L2 and L5 and wherein the second set of satellites have GPS carriers L1 and L2.