GNSS signal processing with known position for reconvergence

• US 9,709,683 B2
• Filed: 03/11/2012
• Issued: 07/18/2017
• Est. Priority Date: 01/14/2008
• Status: Active Grant

• Current Assignee: Trimble Inc.
• Original Assignee: Trimble Inc.
• Inventors: Leandro, Rodrigo, Vollath, Ulrich, Talbot, Nicholas Charles
• Primary Examiner(s): Nguyen, Chuong P
• Application Number:
  US14/002,716
• Publication Number:
  US 20140002300A1
• Time in Patent Office: 1,955 Days
• Field of Search: 34235726, 34235727, 34235744, 34235746
• CPC Class Codes: G01S 19/04 providing carrier phase data
• 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 19/072 Ionosphere corrections
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• 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 provide for positioning of a rover antenna from GNSS data derived from multi-frequency signals and correction data derived from a network of reference stations. At each of a plurality of epochs, the GNSS data and correction data are used to estimate values defining a rover antenna position and a set of multi-frequency ambiguities. An ionospheric-free carrier-phase ambiguity per satellite is estimated based on a known rover antenna position. The estimated ionospheric-free carrier-phase ambiguity is combined with an estimated widelane ambiguity and with an estimated ionospheric-free ambiguity and with values defining the known rover antenna position to obtain values defining an aided rover antenna position and aided multi-frequency ambiguities.

Claims

1. A method of estimating a position of a rover antenna using a computer processor, the method comprising:

obtaining GNSS data derived from multi-frequency signals received at the rover antenna;

obtaining correction data for the GNSS data from a network of reference stations;

at each of a plurality of epochs, estimating values defining a rover antenna position and a set of multi-frequency ambiguities using the GNSS data and the correction data;

estimating an ionospheric-free carrier-phase ambiguity per satellite based on a known rover antenna position; and

assisting determination of an aided rover antenna position using the estimated ionospheric-free carrier-phase ambiguities.

2. The method of claim 1, wherein assisting the determination of the aided rover antenna position comprises combining the estimated ionospheric-free carrier-phase ambiguity with an estimated widelane ambiguity, an estimated ionospheric-free ambiguity, and values defining the known rover antenna position to obtain values defining the aided rover antenna position and aided multi-frequency ambiguities.

3. The method of claim 2, wherein the widelane ambiguities are estimated in a set of code-carrier filters operated by the processor.

4. The method of claim 2, wherein the ionospheric-free ambiguities are estimated in a geometry filter operated by the processor.

5. The method of claim 1, further comprising monitoring precision of an unaided rover antenna position estimate to determine when substantially no further benefit is obtained from using the estimated ionospheric-free carrier-phase ambiguities in assisting determination of the aided rover antenna position.

6. The method of claim 1, wherein the ionospheric-free carrier-phase ambiguity per satellite is computed using the known rover antenna position and observed carrier-phase measurements.

7. The method of claim 1, further comprising improving the ionospheric-free carrier-phase ambiguity for at least one satellite based on the known rover antenna position using a prevailing tropospheric bias on the respective satellite.

8. The method of claim 1, wherein assisting the determination of the aided rover antenna position comprises using the estimated ionospheric-free carrier-phase ambiguity estimates with estimates of other parameters from a set of factorized filters.

9. The method of claim 8, further comprising substituting the ionospheric-free carrier-phase ambiguity estimates for estimates from a bank of auxiliary code-carrier filters.

10. The method of claim 9, further comprising creating separate bank of auxiliary code carrier filter results for the known position results so that normal auxiliary code carrier filter results remain unaffected.

11. A computer program product comprising a non-transitory computer-readable medium embodying instructions for causing an apparatus to perform the method of claim 1.

12. An apparatus comprising:

a receiver configured to;

receive GNSS data derived from multi-frequency signals received at a rover antenna; and

receive correction data for the GNSS data from a network of reference stations; and

a processor coupled to the receiver and configured to;

at each of a plurality of epochs, estimate values defining a rover antenna position and a set of multi-frequency ambiguities using the GNSS data and the correction data;

estimate an ionospheric-free carrier-phase ambiguity per satellite based on a known rover antenna position; and

assist determination of an aided rover antenna position using the estimated ionospheric-free carrier-phase ambiguities.

13. The apparatus of claim 12, wherein assisting determination comprises combining the estimated ionospheric-free carrier-phase ambiguity with an estimated widelane ambiguity, an estimated ionospheric-free ambiguity, and values defining the known rover antenna position to obtain values defining the aided rover antenna position and aided multi-frequency ambiguities.

14. The apparatus of claim 13, wherein the widelane ambiguities are estimated in a set of code-carrier filters operated by the processor.

15. The apparatus of claim 13, wherein the ionospheric-free ambiguities are estimated in a geometry filter operated by the processor.

16. The apparatus of claim 13, wherein the processor is configured to estimate the ionospheric-free carrier-phase ambiguity per satellite using the known rover antenna position and observed carrier-phase measurements.

17. The apparatus of claim 12, wherein the processor is further configured to monitor precision of an unaided rover antenna position estimate to determine when substantially no further benefit is obtained from using the estimated ionospheric-free carrier-phase ambiguities in assisting determination of an aided rover antenna position.

18. The apparatus of claim 12, wherein the processor is further configured to improve the ionospheric-free carrier-phase ambiguity for at least one satellite based on the known rover antenna position using a prevailing tropospheric bias on the respective satellite.

19. The apparatus of claim 12, wherein assisting determination comprises using the estimated ionospheric-free carrier-phase ambiguity estimates with estimates of other parameters from a set of factorized filters operated by the processor.

20. The apparatus of claim 12, wherein the processor is further configured to substitute the ionospheric-free carrier-phase ambiguity estimates for estimates from a bank of auxiliary code-carrier filters.

21. The apparatus of claim 20, wherein the processor is further configured to create a separate bank of auxiliary code carrier filter results for the known position results so that normal auxiliary code carrier filter results remain unaffected.