Position estimation methods and apparatus

• US 8,587,475 B2
• Filed: 10/05/2009
• Issued: 11/19/2013
• Est. Priority Date: 10/06/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Leandro, Rodrigo
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/122,214
• Publication Number:
  US 20110187590A1
• Time in Patent Office: 1,506 Days
• Field of Search: 342/357.27
• US Class Current: 342/357.27
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry

Abstract

A method of determining the position of a GNSS receiver antenna includes steps of acquiring input data which includes observations at the GNSS receiver antenna of signals of at least clock and position information of GNSS satellites, for each of a plurality of epochs. Float parameters of a state vector from the input data of each epoch are then estimated. The float parameters include receiver antenna position, receiver clock, and at least one ambiguity per satellite. A jump in the at least one ambiguity of at least one satellite from one epoch to another epoch is detected. Then bridge parameters from the input data of at least one epoch and from the estimated float parameters are estimated. The bridge parameters include values sufficient to update the float parameters to compensate for the jump, and the bridge parameters are then used to update the float parameters.

Claims

1. A method of determining position of a GNSS receiver antenna, comprising:

a. operating an engine to acquire input data for each of a plurality of epochs, the input data comprising observations at the GNSS receiver antenna of signals of GNSS satellites, and clock and position information for each of the satellites,

b. operating a recursive filter to estimate float parameters of a state vector from the input data of each epoch, the float parameters comprising receiver antenna position, receiver clock, and at least one ambiguity per satellite,

c. operating a jump detector to detect a jump in the at least one ambiguity of at least one satellite from one epoch to another epoch,

d. operating a bridge estimator to estimate bridge parameters from the input data of at least one epoch and from the estimated float parameters, the bridge parameters comprising values sufficient to update the float parameters to compensate for the jump, and

e. using the bridge parameters to update the float parameters.

2. The method of claim 1, wherein the observations comprise observations of signals of at least four GNSS satellites at least until initial values of the float parameters have been estimated.

3. The method of claim 1, wherein the observations comprise raw code and carrier observations for each of at least two frequencies per satellite.

4. The method of claim 1, wherein the observations comprise observations of satellites of at least one of the GPS, GLONASS, Galileo and Compass systems.

5. The method of claim 1, wherein the observations comprise GPS observations of L1 code, L2 code, L1 carrier and L2 carrier.

6. The method of claim 1, wherein the at least one ambiguity per satellite comprises at least one of an iono-free ambiguity per satellite, a separate ambiguity per frequency per satellite, and a widelane ambiguity and a narrowlane ambiguity per satellite.

7. The method of claim 1, wherein raw observations are converted to Wide-Lane and Narrow-Lane observations.

8. The method of claim 1, wherein the input data comprises at least one of broadcast ephemeris data and precision ephemeris data.

9. The method of claim 1, wherein ephemeris data are converted to satellite position and satellite clock for each epoch.

10. The method of claim 1, wherein the float parameters further comprise at least one of tropospheric delay, multipath, and unmodeled error.

11. The method of claim 1, wherein the recursive filter comprises one of a least squares filter and a Kalman filter.

12. The method of claim 1, wherein the at least one estimated ambiguity for each satellite remains constant from epoch to epoch when satellites are continuously tracked, and wherein a jump in at least one estimated ambiguity of at least one satellite from one epoch to another epoch indicates loss of tracking of said at least one satellite.

13. The method of claim 1, wherein the jump detector compares the estimated iono-free ambiguities of one epoch with the estimated iono-free ambiguities of a prior epoch.

14. The method of claim 1, wherein the bridge estimator computes a wide-lane ambiguity jump δ

N_w for at least one satellite.

15. The method of claim 1, wherein the bridge estimator estimates a wide-lane ambiguity jump δ

N_w for at least one satellite and an updated iono-free ambiguity for at least one satellite.

16. The method of claim 15, wherein the bridge estimator estimates a geometry-free ambiguity jump δ

N_gf for at least one satellite.

17. The method of claim 16, wherein the bridge estimator estimates a wide-lane ambiguity jump δ

N_w for at least one satellite and combines the widelane ambiguity jump δ

N_w for at least one satellite with a respective geometry-free ambiguity jump δ

N_gf for at least one satellite to obtain an iono-free ambiguity jump δ

Ni_f for at least one satellite.

18. The method of claim 17, wherein the bridge estimator combines the iono-free ambiguity jump δ

Ni_f for at least one satellite with a respective iono-free ambiguity N_if1 estimated from a pre-jump epoch to obtain an updated iono-free ambiguity Ni_f2 for at least one satellite.

19. The method of claim 1, wherein the bridge estimator estimates an updated receiver antenna position.

20. The method of claim 19, wherein the bridge estimator estimates a wide-lane ambiguity jump δ

N_w for at least one satellite.

21. The method of claim 20, wherein the bridge estimator determines from the wide-lane ambiguity jump δ

N_w for at least one satellite a receiver antenna position jump (δ

X, δ

Y, δ

Z).

22. The method of claim 21, wherein the bridge estimator combines the receiver antenna position jump (δ

X, δ

Y, δ

Z) with a pre-jump receiver antenna position (X₁, Y₁, Z₁) to obtain an updated receiver antenna position (X₂, Y₂, Z₂).

23. The method of claim 1, wherein using the bridge parameters to update the float parameters comprises replacing at least one iono-free ambiguity N_if1 estimated from a pre-jump epoch with a respective updated iono-free ambiguity Ni_f2 for at least one satellite.

24. The method of claim 1, wherein using the bridge parameters to update the float parameters comprises replacing a receiver antenna position (X₁, Y₁, Z₁) estimated from a pre-jump epoch with an updated receiver antenna position (X₂, Y₂, Z₂).

25. The method of claim 1, wherein after using the bridge parameters to update the float parameters, the recursive filter uses the updated float parameters with input data for a subsequent epoch to estimate the float parameters for the subsequent epoch.

52. A non-transitory computer-readable medium embodying a computer program comprising instructions configured, when executed on a computer processing unit, to carry out a method according to claim 1.

26. Apparatus for determining position of a GNSS receiver antenna, comprising:

an engine to acquire input data for each of a plurality of epochs, the input data comprising observations at a GNSS receiver antenna of GNSS satellites, and clock and position information for each of the satellites,

a recursive filter to estimate float parameters of a state vector from the input data of each epoch, the float parameters comprising receiver antenna position, receiver clock, and at least one ambiguity per satellite,

a jump detector to detect a jump in the at least one ambiguity of at least one satellite from one epoch to another epoch,

a bridge estimator to estimate bridge parameters from the input data of at least one epoch and from the estimated float parameters, the bridge parameters comprising values sufficient to update the float parameters to compensate for the jump, and

a float parameter updater to update the float parameters using the bridge.

27. The apparatus of claim 26, wherein the observations comprise observations of at least four GNSS satellites at least until initial estimates of the float parameters have been estimated.

28. The apparatus of claim 26, wherein the observations comprise raw code and carrier observations for each of at least two frequencies per satellite.

29. The apparatus of claim 26, wherein the observations comprise observations of satellites of at least one of the GPS, GLONASS, Galileo and Compass systems.

30. The apparatus of claim 26, wherein the observations comprise GPS observations of L1 code, L2 code, L1 carrier and L2 carrier.

31. The apparatus of claim 26, wherein the at least one ambiguity per satellite comprises at least one of an iono-free ambiguity per satellite, a eparate ambiguity per frequency per satellite, and a widelane ambiguity and a narrowlane ambiguity per satellite.

32. The apparatus of claim 26, further comprising a converter element to convert raw observations into Wide-Lane observations and Narrow-Lane observations.

33. The apparatus of claim 26, wherein the engine to acquire input data is adapted to acquire at least one of broadcast ephemeris data and precision ephemeris data.

34. The apparatus of claim 26, further comprising a converter element to convert ephemeris data into satellite position and satellite clock for each epoch.

35. The apparatus of claim 26, wherein the float parameters further comprise at least one of tropospheric delay, multipath, and unmodeled error.

36. The apparatus of claim 26, wherein the recursive filter comprises one of a least squares filter and a Kalman filter.

37. The apparatus of claim 26, wherein the at least one estimated ambiguity for each satellite remains constant from epoch to epoch when satellites are continuously tracked, and wherein a jump in at least one estimated ambiguity of at least one satellite from one epoch to another epoch indicates loss of tracking of said at least one satellite.

38. The apparatus of one of claims 26-37 claim 26, wherein the jump detector is adapted to compare the estimated iono-free ambiguities of one epoch with the estimated iono-free ambiguities of a prior epoch.

39. The apparatus of claim 26, wherein the bridge estimator is adapted to compute a wide-lane ambiguity jump δ

N_w for at least one satellite.

40. The apparatus of claim 26, wherein the bridge estimator is adapted to estimate a wide-lane ambiguity jump δ

N_w for at least one satellite and an updated iono-free ambiguity for at least one satellite.

41. The apparatus of claim 26, wherein the bridge estimator is adapted to estimate a geometry-free ambiguity jump δ

N_gf for at least one satellite.

42. The apparatus of claim 26, wherein the bridge estimator is adapted to compute a wide-lane ambiguity jump δ

N_w for at least one satellite and to ombine the widelane ambiguity jump δ

N_w for at least one satellite with a respective geometry-free ambiguity jump δ

N_gf for at least one satellite to obtain an iono-free ambiguity jump δ

Ni_f for at least one satellite.

43. The apparatus of claim 26, wherein the bridge estimator is adapted to combine the iono-free ambiguity jump δ

Ni_f for at least one satellite with a respective iono-free ambiguity N_if1 estimated from a pre-jump epoch to obtain an updated iono-free ambiguity Ni_f2 for at least one satellite.

44. The apparatus of claim 26, wherein the bridge estimator is adapted to estimate an updated receiver antenna position.

45. The apparatus of claim 44, wherein the bridge estimator is adapted to compute a wide-lane ambiguity jump δ

N_w for at least one satellite.

46. The apparatus of claim 45, wherein the bridge estimator is adapted to determine from the wide-lane ambiguity jump δ

N_w for at least one satellite a receiver antenna position jump (δ

X, δ

Y, δ

Z).

47. The apparatus of claim 46, wherein the bridge estimator is adapted to combine the receiver antenna position jump (δ

X, δ

Y, δ

Z) with a pre-jump receiver antenna position (X₁, Y₁, Z₁) to obtain an updated receiver antenna position (X₂, Y₂, Z₂).

48. The apparatus of claim 26, wherein the float parameter updater is adapted to replace at least one iono-free ambiguity N_if1 estimated from a pre-jump epoch with a respective updated iono-free ambiguity Ni_f2 for at least one satellite.

49. The apparatus of claim 26, wherein the float parameter updater is adapted to replace a receiver antenna position (X₁, Y₁, Z₁) estimated from a pre-jump epoch with an updated receiver antenna position (X₂, Y₂, Z₂).

50. The apparatus of claim 26, wherein the recursive filter uses the updated float parameters with input data for a subsequent epoch to estimate the float parameters for the subsequent epoch.

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