GNSS Signal Processing to Estimate Phase-Leveled Clocks

• US 20120162007A1
• Filed: 09/19/2010
• Published: 06/28/2012
• Est. Priority Date: 06/22/2007
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Leandro, Rodrigo, Glocker, Markus, Seeger, Stephan
• Granted Patent: US 9,157,999 B2
• Time in Patent Office: Days
• US Class Current: 342/357.42
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• 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 are described for processing a set of GNSS signal data derived from code observations and carrier-phase observations at multiple receivers of GNSS signals of multiple satellites over multiple epochs, the GNSS signals having at least two carrier frequencies and a navigation message containing orbit information, comprising: obtaining precise orbit information for each satellite, determining at least one set of ambiguities per receiver, each ambiguity corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and using at least the precise orbit information, the ambiguities and the GNSS signal data to estimate a phase-leveled clock per satellite.

Claims

1. A method of processing a set of GNSS signal data derived from code observations and carrier-phase observations at multiple receivers of GNSS signals of multiple satellites over multiple epochs, the GNSS signals having at least two carrier frequencies and a navigation message containing orbit information, comprising:

obtaining precise orbit information for each satellite,

determining at least one set of ambiguities per receiver, each ambiguity corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and

using at least the precise orbit information, the ambiguities and the GNSS signal data to estimate a phase-leveled clock per satellite.

2. The method of claim 1, wherein determining ambiguities is performed at a first rate and wherein estimating a phase-leveled clock per satellite is performed at a second rate higher than the first rate.

3. The method of claim 1, wherein estimating the phase-leveled clock per satellite comprises:

using at least the precise orbit information, the ambiguities and the GNSS signal data to estimate a set of phase-leveled clocks per receiver, each phase-leveled clock corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and

using a plurality of the phase-leveled clocks to estimate one phase-leveled clock per satellite.

4. The method of claim 1, wherein determining the ambiguities comprises using at least one phase-leveled clock per satellite previously estimated to estimate the ambiguities.

5. The method of claim 1, further comprising obtaining at least one additional phase-leveled clock per satellite estimated from an external source, and wherein determining the ambiguities comprises using said at least one additional phase-leveled clock per satellite to estimate the ambiguities.

6. The method of claim 1, further comprising

determining at least one set of ambiguities per receiver for additional receivers, each ambiguity corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link,

after determining the ambiguities for the additional receivers, using at least the precise orbit information, the ambiguities for the additional receivers and the GNSS signal data to estimate the at least one additional phase-leveled clock per satellite.

7. The method of claim 1, wherein the at least two carrier frequencies comprise at least two of the GPS L1, GPS L2 and GPS L5 frequencies.

8. The method of claim 1, wherein determining at least one set of ambiguities per receiver comprises at least one of:

estimating float ambiguity values, estimating float ambiguity values and fixing the float ambiguity values to integer values, estimating float ambiguity values and forming at least one weighted average of integer value candidates, and constraining the ambiguity values in a sequential filter.

9. The method of claim 1, wherein the ambiguities are undifferenced between satellites.

10. The method of claim 1, wherein the ambiguities are single-differenced between satellites.

21. An article of manufacture comprising a tangible medium embodying instructions configured, when executed on a computer processing unit, to carry out a method according to claim 1.

11. Apparatus for processing a set of GNSS signal data derived from code observations and carrier-phase observations at multiple receivers of GNSS signals of multiple satellites over multiple epochs, the GNSS signals having at least two carrier frequencies and a navigation message containing orbit information, comprising:

an element to obtain precise orbit information for each satellite,

an element to determine at least one set of ambiguities per receiver, each ambiguity corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and

an element using at least the precise orbit information, the ambiguities and the GNSS signal data to estimate a phase-leveled clock per satellite.

12. The apparatus of claim 11, wherein the ambiguities are determined at a first rate and wherein the phase-leveled clock per satellite is determined at a second rate higher than the first rate.

13. The apparatus of claim 11, wherein the element to estimate the phase-leveled clock per satellite is adapted to use at least the precise orbit information, the ambiguities and the GNSS signal data to estimate a set of phase-leveled clocks per receiver, each phase-leveled clock corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and to use a plurality of the phase-leveled clocks to estimate one phase-leveled clock per satellite.

14. The apparatus of claim 11, wherein the ambiguities are estimated using at least one previously-estimated phase-leveled clock per satellite.

15. The apparatus of claim 11, wherein the ambiguities are estimated using at least one additional phase-leveled clock per satellite obtained from an external source.

16. The apparatus of claim 11, wherein the element for determining ambiguities is adapted to determine at least one set of ambiguities per receiver for additional receivers, each ambiguity corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and wherein the element to estimate a phase-leveled clock per satellite is adapted to use at least the precise orbit information, the ambiguities for the additional receivers and the GNSS signal data to estimate at least one additional phase-leveled clock per satellite.

17. The apparatus of claim 11, wherein the at least two carrier frequencies comprise at least two of the GPS L1, GPS L2 and GPS L5 frequencies.

18. The apparatus of claim 11, wherein the element to determine at least one set of ambiguities per receiver is adapted to at least one of:

estimate float ambiguity values, estimate float ambiguity values and fix the float ambiguity values to integer values, estimate float ambiguity values and form at least one weighted average of integer value candidates, and constrain the ambiguity values in a sequential filter.

19. The apparatus of claim 11, wherein the ambiguities are undifferenced between satellites.

20. The apparatus of claim 11, wherein the ambiguities are single-differenced between satellites.

22. (canceled)