GNSS signal processing methods and apparatus

• US 8,717,237 B2
• Filed: 04/26/2010
• Issued: 05/06/2014
• Est. Priority Date: 05/02/2009
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Vollath, Ulrich
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/263,072
• Publication Number:
  US 20120026038A1
• Time in Patent Office: 1,471 Days
• Field of Search: 342/450
• US Class Current: 342/450
• CPC Class Codes: G01S 19/13 Receivers
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude

Abstract

Methods and apparatus are provided for processing a set of GNSS signal data derived from observations of GNSS signals of multiple transmitters over multiple epochs, the GNSS signals having a first signal and a second signal in a first band which can be tracked as a single wide-band signal and each of which can be tracked separately, comprising: obtaining carrier-phase observations of the first signal, obtaining carrier-phase observations of the second signal, obtaining code observations of the wide-band signal, and estimating from a set of observables comprising the carrier-phase observations of the first signal, the carrier-phase observations of the second signal and the code observations of the wide-band signal values for a set of parameters comprising: position of a receiver of the GNSS signals, clock error of a receiver of the GNSS signals, and an array of ambiguities comprising an ambiguity for each transmitter from which carrier-phase observations of the first signal are obtained and an ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained.

Claims

1. A method of processing a set of GNSS signal data derived from observations of GNSS signals of multiple transmitters over multiple epochs, the GNSS signals having a first signal and a second signal in a first band which can be tracked as a single wide-band signal and each of which can be tracked separately, comprising:

a. obtaining carrier-phase observations of the first signal,

b. obtaining carrier-phase observations of the second signal,

c. obtaining code observations of the wide-band signal, and

d. estimating from a set of observables comprising the carrier-phase observations of the first signal, the carrier-phase observations of the second signal and the code observations of the wide-band signal values for a set of parameters comprising;

position of a receiver of the GNSS signals, clock error of a receiver of the GNSS signals, and an array of ambiguities comprising an ambiguity for each transmitter from which carrier-phase observations of the first signal are obtained and an ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained.

2. The method of claim 1, wherein the first signal and the second signal are respective spectral components of a single alternate binary offset carrier modulation.

3. The method of claim 1, wherein the first band is the Galileo E5 band, the single wide-band signal is the Galileo E5ab signal, the first signal is the Galileo E5a signal and the second signal is the Galileo Eb5 signal.

4. The method of claim 1, wherein the GNSS signals have a third signal in a second band, wherein the method further comprises obtaining carrier-phase observations of the third signal, wherein the set of observables further comprises the carrier-phase observations of the third signal, and wherein the array of ambiguities further comprises an ambiguity for each transmitter from which carrier-phase observations of the third signal are obtained.

5. The method of claim 4, wherein the second band is the Galileo E2-L1-E1 band and the third signal is the Galileo E1 signal.

6. The method of claim 1, further comprising obtaining carrier-phase observations of the wide-band signal, wherein the set of observables further comprises the carrier-phase observations of the wide-band signal, and wherein the array of ambiguities further comprises an ambiguity for each transmitter from which carrier-phase observations of the wide-band signal are obtained.

7. The method of claim 1, wherein the GNSS signals have a fourth signal in a third band, wherein the method further comprises obtaining carrier-phase observations of the fourth signal, wherein the set of observables further comprises the carrier-phase observations of the fourth signal, and wherein the array of ambiguities further comprises an ambiguity for each transmitter from which carrier-phase observations of the fourth signal are obtained.

8. The method of claim 7, wherein the third band is the Galileo E6 band and the fourth signal is the Galileo E6 signal.

9. The method of claim 1, wherein the method further comprises obtaining code observations of the first signal, and wherein the set of observables further comprises the code observations of the first signal.

10. The method of claim 1, wherein the method further comprises obtaining code observations of the second signal, and wherein the set of observables further comprises the code observations of the second signal.

11. The method of claim 1, wherein the method further comprises obtaining code observations of the third signal, and wherein the set of observables further comprises the code observations of the third signal.

12. The method of claim 1, wherein the method further comprises obtaining code observations of the fourth signal, and wherein the set of observables further comprises the code observations of the fourth signal.

13. The method of claim 1, wherein estimating the set of parameters comprises applying to the set of observation a filter having a plurality of states corresponding to parameters of the set of parameters.

14. The method of claim 1, wherein estimating the set of parameters comprises:

i. applying to the set of observations a geometry filter using a geometry carrier-phase combination to obtain an array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information;

ii. applying to the set of GNSS signal data a bank of geometry-free filters using geometry-free combinations to obtain an array of ambiguity estimates for the geometry-free combinations and associated statistical information; and

iii. combining the array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information with the array of ambiguity estimates for the geometry-free carrier-phase combinations and associated statistical information to obtain a combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

15. The method of claim 1, wherein estimating the set of parameters comprises:

i. applying to the set of observations a geometry filter using a geometry carrier-phase combination to obtain an array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information;

ii. applying to the set of GNSS signal data a bank of ionosphere filters using a geometry-free ionosphere carrier-phase combination to obtain an array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information;

iii. applying to the set of GNSS signal data at least one code filter using a plurality of geometry-free code-carrier combinations to obtain an array of ambiguity estimates for the code-carrier combinations and associated statistical information; and

iv. combining the array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information with the array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information and the array of ambiguity estimates for the code-carrier combinations and associated statistical information to obtain a combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

16. The method of claim 4, wherein estimating the set of parameters comprises:

i. applying to the set of observations a geometry filter using a geometry carrier-phase combination to obtain an array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information;

ii. applying to the set of GNSS signal data a bank of ionosphere filters using a geometry-free ionosphere carrier-phase combination to obtain an array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information;

iii. applying to the set of GNSS signal data at least one bank of supplemental (Quintessence, or “

Q”

) filters using a geometry-free and ionosphere-free carrier-phase combination to obtain an array of ambiguity estimates for the geometry-free and ionosphere-free carrier-phase combination and associated statistical information;

iv. applying to the set of GNSS signal data at least one code filter using a plurality of geometry-free code-carrier combinations to obtain an array of ambiguity estimates for the code-carrier combinations and associated statistical information; and

v. combining the array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information with the array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information and the array of ambiguity estimates for the geometry-free and ionosphere-free carrier-phase combination and associated statistical information and the array of ambiguity estimates for the code-carrier combinations and associated statistical information to obtain a combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

17. The method of claim 1, wherein the ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained is a float value, and wherein the method further comprises reporting the estimated position of the receiver.

18. The method of claim 1, wherein the ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained is a float value, the method further comprising:

fixing at least a subset of the array of ambiguities as integer values, and reporting the estimated position of the receiver.

19. The method of claim 1, wherein the ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained is a float value, the method further comprising:

assigning integer values to at least a subset of the array of ambiguities to define a plurality of candidate sets;

determining a quality measure for each of the candidate sets; and

obtaining a weighted average of at least a subset of the candidate sets in which each candidate set of the weighted average is weighted based on its quality measure.

20. The method of claim 1, further comprising applying corrections to the observations prior to estimating the set of parameters from the set of observables.

21. The method of claim 20, wherein the observations comprise observations of GNSS signals acquired at a rover receiver and the corrections comprise observations of GNSS signals acquired at a reference receiver, wherein applying corrections to the observations comprises combining the observations acquired at the rover receiver with the observations acquired at the reference receiver to obtain differential observations, wherein estimating values for the set of parameters comprises estimating the values from the differential observations, and wherein estimating values for the set of parameters comprises estimating a position of the rover receiver.

22. The method of claim 20, wherein the observations comprise observations of GNSS signals acquired at a rover receiver and the corrections are derived from observations of GNSS signals acquired at a plurality of reference receivers, wherein applying corrections to the observations comprises combining the observations acquired at the rover receiver with the virtual reference station data to obtain network-corrected observations, wherein estimating values for the set of parameters comprises estimating the values from the network-corrected observations, and wherein estimating values for the set of parameters comprises estimating a position of the rover receiver.

23. The method of claim 20, wherein the observations comprise observations of GNSS signals acquired at a rover receiver, wherein the corrections comprise satellite orbit data and satellite clock data, wherein applying corrections to the observations comprises combining the observations acquired at the rover receiver with the satellite orbit data and the satellite clock data to obtain corrected observations, wherein estimating values for the set of parameters comprises estimating the values from the corrected observations, and wherein estimating values for the set of parameters comprises estimating a position of the rover receiver.

24. The method of claim 1, wherein estimating values for the set of parameters is performed substantially in real time.

25. The method of claim 1, wherein estimating values for the set of parameters is performed in a post-processing operation which is not substantially in real time.

53. A computer program comprising instructions configured, when executed on a computer processing unit, to carry out a method according to claim 1.

54. A computer-readable medium comprising a computer program according to claim 53.

26. Apparatus for processing a set of GNSS signal data derived from observations of GNSS signals of multiple transmitters over multiple epochs, the GNSS signals having a first signal and a second signal in a first band which can be tracked as a single wide-band signal and each of which can be tracked separately, comprising:

a. an element to obtain carrier-phase observations of the first signal,

b. an element to obtain carrier-phase observations of the second signal,

c. an element to obtain code observations of the wide-band signal, and

d. a filtering element to estimate from a set of observables comprising the carrier-phase observations of the first signal, the carrier-phase observations of the second signal and the code observations of the wide-band signal values for a set of parameters comprising;

position of a receiver of the GNSS signals, clock error of a receiver of the GNSS signals, and an array of ambiguities comprising an ambiguity for each transmitter from which carrier-phase observations of the first signal are obtained and an ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained.

27. The apparatus of claim 26, wherein the first signal and the second signal are respective spectral components of a single alternate binary offset carrier modulation.

28. The apparatus of claim 26, wherein the first band is the Galileo E5 band, the single wide-band signal is the Galileo E5ab signal, the first signal is the Galileo E5a signal and the second signal is the Galileo Eb5 signal.

29. The apparatus of claim 26, wherein the GNSS signals have a third signal in a second band, wherein the apparatus further comprises an element to obtain carrier-phase observations of the third signal, wherein the set of observables further comprises the carrier-phase observations of the third signal, and wherein the array of ambiguities further comprises an ambiguity for each transmitter from which carrier-phase observations of the third signal are obtained.

30. The apparatus of claim 29, wherein the second band is the Galileo E2-L1-E1 band and the third signal is the Galileo E1 signal.

31. The apparatus of claim 26, further comprising an element to obtain carrier-phase observations of the wide-band signal, wherein the set of observables further comprises the carrier-phase observations of the wide-band signal, and wherein the array of ambiguities further comprises an ambiguity for each transmitter from which carrier-phase observations of the wide-band signal are obtained.

32. The apparatus of claim 26, wherein the GNSS signals have a fourth signal in a third band, wherein the apparatus further comprises an element to obtain carrier-phase observations of the fourth signal, wherein the set of observables further comprises the carrier-phase observations of the fourth signal, and wherein the array of ambiguities further comprises an ambiguity for each transmitter from which carrier-phase observations of the fourth signal are obtained.

33. The apparatus of claim 32, wherein the third band is the Galileo E6 band and the fourth signal is the Galileo E6 signal.

34. The apparatus of claim 26, wherein the apparatus further comprises an element to obtain code observations of the first signal, and wherein the set of observables further comprises the code observations of the first signal.

35. The apparatus of claim 26, wherein the apparatus further comprises obtaining code observations of the second signal, and wherein the set of observables further comprises the code observations of the second signal.

36. The apparatus of claim 26, wherein the apparatus further comprises an element to obtain code observations of the third signal, and wherein the set of observables further comprises the code observations of the third signal.

37. The apparatus of claim 26, wherein the apparatus further comprises an element to obtain code observations of the fourth signal, and wherein the set of observables further comprises the code observations of the fourth signal.

38. The apparatus of claim 26, wherein the filtering element comprises a filter having a plurality of states corresponding to parameters of the set of parameters.

39. The apparatus of claim 26, wherein the filtering element comprises:

i. a geometry filter using a geometry carrier-phase combination to obtain an array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information;

ii. a bank of geometry-free filters using geometry-free combinations to obtain an array of ambiguity estimates for the geometry-free combinations and associated statistical information; and

iii. a combining element to combine the array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information with the array of ambiguity estimates for the geometry-free carrier-phase combinations and associated statistical information to obtain a combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

40. The apparatus of claim 26, wherein the filtering element comprises:

i. a geometry filter using a geometry carrier-phase combination to obtain an array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information;

ii. a bank of ionosphere filters using a geometry-free ionosphere carrier-phase combination to obtain an array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information;

iii. at least one code filter using a plurality of geometry-free code-carrier combinations to obtain an array of ambiguity estimates for the code-carrier combinations and associated statistical information; and

iv. a combining element to combine the array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information with the array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information and the array of ambiguity estimates for the code-carrier combinations and associated statistical information to obtain a combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

41. The apparatus of claim 29, wherein the filtering element comprises:

v. a geometry filter using a geometry carrier-phase combination to obtain an array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information;

vi. a bank of ionosphere filters using a geometry-free ionosphere carrier-phase combination to obtain an array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information;

vii. at least one bank of supplemental (Quintessence, or “

Q”

) filters using a geometry-free and ionosphere-free carrier-phase combination to obtain an array of ambiguity estimates for the geometry-free and ionosphere-free carrier-phase combination and associated statistical information;

viii. at least one code filter using a plurality of geometry-free code-carrier combinations to obtain an array of ambiguity estimates for the code-carrier combinations and associated statistical information; and

ix. a combining element to combine the array of ambiguity estimates for the geometry carrier-phase combination and associated statistical information with the array of ambiguity estimates for the ionosphere carrier-phase combination and associated statistical information and the array of ambiguity estimates for the geometry-free and ionosphere-free carrier-phase combination and associated statistical information and the array of ambiguity estimates for the code-carrier combinations and associated statistical information to obtain a combined array of ambiguity estimates for all carrier phase observations and associated statistical information.

42. The apparatus of claim 26, wherein the ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained is a float value, and wherein the apparatus further comprises an element to report the estimated position of the receiver.

43. The apparatus of claim 26, wherein the ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained is a float value, the apparatus further comprising:

a fixing element to fix at least a subset of the array of ambiguities as integer values, and to report the estimated position of the receiver.

44. The apparatus of claim 26, wherein the ambiguity for each transmitter from which carrier-phase observations of the second signal are obtained is a float value, the apparatus further comprising:

an assigning element to assign integer values to at least a subset of the array of ambiguities to define a plurality of candidate sets;

a quality element to determine a quality measure for each of the candidate sets; and

an averaging element to obtain a weighted average of at least a subset of the candidate sets in which each candidate set of the weighted average is weighted based on its quality measure.

45. The apparatus of claim 26, further comprising a correcting element to apply corrections to the observations and to supply corrected observations to the filtering element.

46. The apparatus of claim 45, wherein the observations comprise observations of GNSS signals acquired at a rover receiver and the corrections comprise observations of GNSS signal acquired at a reference receiver, wherein the correcting element is operative to combine observations acquired at the rover receiver with observations acquired at the reference receiver to obtain differential observations, wherein the filtering element is operative to estimate values for the set of parameters from the differential observations, and wherein the filtering element is operative to estimate a position of the rover receiver.

47. The apparatus of claim 45, wherein the observations comprise observations of GNSS signals acquired at a rover receiver and the corrections are derived from observations of GNSS signals acquired at a plurality of reference receivers, wherein the correcting element is operative to combine the observations acquired at the rover receiver with the virtual reference station data to obtain corrected observations, wherein the filtering element is operative to estimate values for the set of parameters from the corrected observations, and wherein the filtering element is operative to estimate a position of the rover receiver.

48. The apparatus of claim 45, wherein the observations comprise observations of GNSS signals acquired at a rover receiver, wherein the corrections comprise satellite orbit data and satellite clock data, wherein the correcting element is operative to combine the observations acquired at the rover receiver with the satellite orbit data and the satellite clock data to obtain corrected observations, wherein the filtering element is operative to estimate values for the set of parameters from the corrected observations, and wherein the filtering element is operative to estimate a position of the rover receiver.

49. The apparatus of claim 26, wherein the filtering element is operative to estimate values for the set of parameters substantially in real time.

50. The apparatus of claim 26, wherein the filtering element is operative to estimate values for the set of parameters in a post-processing operation which is not substantially in real time.

51. A rover receiver including an apparatus according to claim 26.

52. A network station including an apparatus according to claim 26.