GNSS Signal Processing with Rover Ambiguity Fixing

• US 20120154214A1
• Filed: 09/19/2010
• Published: 06/21/2012
• 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
• Granted Patent: US 9,146,319 B2
• Time in Patent Office: Days
• US Class Current: 342/357.27
• 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 signals of a set of satellites having carriers observed at a rover antenna, wherein the data includes a carrier observation and a code observation of each carrier of each satellite, comprising: obtaining for each satellite clock corrections comprising at least two of: (i) a code-leveled satellite clock, (ii) a phase-leveled satellite clock, and (iii) a satellite clock bias representing a difference between a code-leveled satellite clock and a phase-leveled satellite clock, running a first filter which uses at least the GNSS signal data and the satellite clock corrections to estimate values for parameters comprising at least one carrier ambiguity for each satellite, and a covariance matrix of the carrier ambiguities, determining from each carrier ambiguity an integer-nature carrier ambiguity comprising one of: an integer value, and a combination of integer candidates, inserting the integer-nature carrier ambiguities as pseudo-observations into a second filter, and applying the second filter to the GNSS signal data and the satellite clock corrections to obtain estimated values for parameters comprising at least the position of the receiver.

Claims

1. A method of processing a set of GNSS signal data derived from signals of a set of satellites having carriers observed at a rover antenna, wherein the data includes a carrier observation and a code observation of each carrier of each satellite, comprising:

obtaining for each satellite clock corrections comprising at least two of;

(i) a code-leveled satellite clock, (ii) a phase-leveled satellite clock, and (iii) a satellite clock bias representing a difference between a code-leveled satellite clock and a phase-leveled satellite clock,

running a first filter which uses at least the GNSS signal data and the satellite clock corrections to estimate values for parameters comprising at least one carrier ambiguity for each satellite, and a covariance matrix of the carrier ambiguities,

determining from each carrier ambiguity an integer-nature carrier ambiguity comprising one of;

an integer value, and a combination of integer candidates, and

inserting the integer-nature carrier ambiguities as pseudo-observations into a second filter, and applying the second filter to the GNSS signal data and the satellite clock corrections to obtain estimated values for parameters comprising at least the position of the receiver.

2. The method of claim 1, wherein the integer-nature carrier ambiguities are between-satellite single-differenced ambiguities.

3. The method of claim 1, further comprising

obtaining a set of MW corrections,

running a third filter using the GNSS signal data and at least the MW corrections to obtain at least a set of WL ambiguities, and

using the set of WL ambiguities to obtain the integer-nature carrier ambiguity.

4. The method of claim 3, wherein the WL ambiguities comprise at least one of:

float values, integer values, and float values based on integer candidates.

5. The method of claim 4, wherein the covariance matrix of the ambiguities is scaled to reflect the change due to the use of the WL ambiguities.

6. The method of claim 1, wherein the WL ambiguities are between-satellite single-differenced ambiguities.

7. The method of claim 1, wherein the integer-nature ambiguities comprise at least one of:

L1-L2 ionospheric-free ambiguities, L2-L5 ionospheric-free ambiguities, and carrier ambiguities of a linear combination of two or more GNSS frequencies.

8. The method of claim 1, wherein ionospheric delay information is used to feed one or more of the filters and wherein the integer-nature ambiguity comprises at least one of:

carrier ambiguity of L1 frequency, carrier ambiguity of L2 frequency, carrier ambiguity of L5 frequency, and carrier ambiguity of any GNSS frequency.

9. The method of claim 1, wherein the second filter comprises one of:

a new filter, a copy of the first filter, and the first filter.

10. The method of claim 1, wherein the code-leveled satellite clock is used for modeling all GNSS observations, and the float ambiguity is adapted to the level of the phase-leveled clock by applying the difference between the code-leveled satellite clock and the phase-leveled satellite clock.

11. The method of claim 1, wherein the code-leveled satellite clock is used for modeling all GNSS code observations and the phase-leveled satellite clock is used for modeling all GNSS carrier observations.

12. The method of claim 1, wherein determining the integer-nature carrier ambiguity from a float ambiguity comprises at least one of:

rounding the float ambiguity to the nearest integer, choosing best integer candidates from a set of integer candidates generated using integer least squares, and computing float values using a set of integer candidates generated using integer least squares.

13. The method of claim 1, wherein at least one of the first filter and second filter further estimates at least one of:

receiver phase-leveled clock, receiver code-leveled clock, tropospheric delay, receiver clock bias representing a difference between the code-leveled receiver clock and the phase-leveled receiver clock, and multipath states.

14. The method of claim 1, wherein at least one of the first filter, the second filter and the third filter is adapted to update the estimated values for each of a plurality of epochs of GNSS signal data.

29. 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.

15. Apparatus for processing a set of GNSS signal data derived from signals of a set of satellites having carriers observed at a rover antenna, wherein the data includes a carrier observation and a code observation of each carrier of each satellite, comprising:

an element to obtain for each satellite clock corrections comprising at least two of;

(i) a code-leveled satellite clock, (ii) a phase-leveled satellite clock, and (iii) a satellite clock bias representing a difference between a code-leveled satellite clock and a phase-leveled satellite clock,

a first filter using at least the GNSS signal data and the satellite clock corrections to estimate values for parameters comprising at least one carrier ambiguity for each satellite, and a covariance matrix of the carrier ambiguities,

an element to determine from each carrier ambiguity an integer-nature carrier ambiguity comprising one of;

an integer value, and a combination of integer candidates, and

a second filter using the integer-nature carrier ambiguities as pseudo-observations and using the GNSS signal data and the satellite clock corrections to estimate values for parameters comprising at least the position of the receiver.

16. The apparatus of claim 15, wherein the integer-nature carrier ambiguities are between-satellite single-differenced ambiguities.

17. The apparatus of claim 15, further comprising

an element to obtain a set of MW corrections,

a third filter using the GNSS signal data and at least the MW corrections to obtain at least a set of WL ambiguities, and

an element using the set of WL ambiguities to obtain the integer-nature carrier ambiguity.

18. The apparatus of claim 17, wherein the WL ambiguities comprise at least one of:

float values, integer values, and float values based on integer candidates.

19. The apparatus of claim 18, wherein the covariance matrix of the ambiguities is scaled to reflect the change due to the use of the WL ambiguities.

20. The apparatus of claim 15, wherein the WL ambiguities are between-satellite single-differenced ambiguities.

21. The apparatus of claim 15, wherein the integer-nature ambiguities comprise at least one of:

L1-L2 ionospheric-free ambiguities, L2-L5 ionospheric-free ambiguities, and carrier ambiguities of a linear combination of two or more GNSS frequencies.

22. The apparatus of claim 15, wherein one or more of the filters is fed with the ionospheric delay information and wherein the integer-nature ambiguity comprises at least one of:

carrier ambiguity of L1 frequency, carrier ambiguity of L2 frequency, carrier ambiguity of L5 frequency, and carrier ambiguity of any GNSS frequency.

23. The apparatus of claim 15, wherein the second filter comprises one of:

a new filter, a copy of the first filter, and the first filter.

24. The apparatus of claim 15, wherein the code-leveled satellite clock is used for modeling all GNSS observations, and the float ambiguity is adapted to the level of the phase-leveled clock by applying the difference between the code-leveled satellite clock and the phase-leveled satellite clock.

25. The apparatus of claim 15, wherein the code-leveled satellite clock is used for modeling all GNSS code observations and the phase-leveled satellite clock is used for modeling all GNSS carrier observations.

26. The apparatus of claim 15, wherein the element to determine from each carrier ambiguity an integer-nature carrier ambiguity comprises is adapted to perform at least one of:

rounding the float ambiguity to the nearest integer, choosing best integer candidates from a set of integer candidates generated using integer least squares, and computing float values using a set of integer candidates generated using integer least squares.

27. The apparatus of claim 15, wherein at least one of the first filter and the second filter is adapted to further estimate at least one of:

receiver phase-leveled clock, receiver code-leveled clock, tropospheric delay, receiver clock bias representing a difference between the code-leveled receiver clock and the phase-leveled receiver clock, and multipath states.

28. The apparatus of claim 15, wherein at least one of the first filter, the second filter and the third filter is adapted to update the estimated values for each of a plurality of epochs of GNSS signal data.

30. (canceled)