COMBINED CYCLE SLIP INDICATORS FOR REGIONALLY AUGMENTED GNSS

• US 20140002299A1
• Filed: 06/28/2012
• Published: 01/02/2014
• Est. Priority Date: 06/22/2007
• Status: Active Grant

• Current Assignee: Trimble Inc.
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Leandro, Rodrigo, Talbot, Nicholas Charles
• Granted Patent: US 9,651,667 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 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• 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 for determining a precise position of a rover located within a region are presented using rover observations comprising code observations and carrier-phase observations of GNSS signals on at least two carrier frequencies over multiple epochs. Correction data is received for each of the epochs at least one code bias per satellite. Synthetic reference data is generated for each of the epochs from the correction data for a synthetic station location. A determination is made for each epoch whether a cycle slip has occurred. Upon determining that a cycle slip has occurred, values of any variables of a set of state variables which are affected by the cycle slip are reset. Each epoch of rover observations and correction data is used to estimate updated values for the set of state variables including a set of ambiguities and coordinates of a precise rover position.

Claims

1. A method of determining, using a processor, a precise position of a rover located within a region, the method comprising:

a. obtaining rover observations comprising code observations and carrier-phase observations of GNSS signals on at least two carrier frequencies over multiple epochs,

b. receiving correction data comprising for each of the epochs at least one code bias per satellite, at least one of;

(i) a fixed-nature MW bias per satellite or (ii) values from which a fixed-nature MW bias per satellite is derivable, or at least one of;

(iii) an ionospheric delay per satellite for each of multiple regional network stations, (iv) non-ionospheric corrections, or (v) information on the corrections continuity for one or more correction components;

c. applying the correction data to the rover data using one of (i) creating synthetic reference data for each of the epochs from the correction data for a synthetic station location or (ii) directly correcting the rover measurements with the received corrections,

d. determining, using the processor, for each epoch whether a cycle slip has occurred in at least one of (i) the rover observations or (ii) observations at network stations used to prepare the correction data,

e. upon determining that a cycle slip has occurred, resetting values of any variables of a set of state variables which are affected by the cycle slip while retaining values of at least some variables of the set which are not affected by the cycle slip, and

f. using each epoch of rover observations and correction data to estimate updated values for the set of state variables, the state variables comprising a set of ambiguities and coordinates of a precise rover position.

2. The method of claim 1, wherein the correction data comprises at least one cycle slip indicator, and wherein state variables affected by the cycle slip are determined from the at least one cycle slip indicator.

3. The method of claim 1, wherein the correction data comprises at least one ionospheric-free cycle slip indicator per satellite for a plurality of satellites, wherein determining whether a cycle slip has occurred comprises monitoring the ionospheric-free cycle slip indicators to determine an identity of at least one satellite for which an ionospheric-free cycle slip has occurred, and wherein resetting state variables comprises resetting state variables affected by the ionospheric-free cycle slip.

4. The method of claim 1, wherein the correction data comprises at least one ionospheric cycle slip indicator per satellite per station of a network from which the correction data arc derived, wherein determining whether a cycle slip has occurred comprises monitoring the ionospheric cycle slip indicators to determine an identity of at least one satellite-station pair for which an ionospheric cycle slip has occurred, and wherein resetting state variables comprises resetting state variables affected by the at least one ionospheric cycle slip.

5. The method of claim 1, wherein using each epoch of rover observations and correction data to estimate updated values for the set of state variables comprises applying a factorized array of recursive filters comprising a code-carrier filter bank using a Melbourne-Wuebbena code-carrier combination, a an ionospheric filter bank using an ionospheric carrier combination, and a geometry filter using an ionospheric-free carrier combination.

6. The method of claim 5, wherein determining that a cycle slip has occurred comprises monitoring an ionospheric-free cycle slip indicator per satellite to identify an ionospheric-free cycle slip as to a specific satellite, and wherein resetting values of any variables of a set of state variables which are affected by the cycle slip comprises resetting the value of an ionospheric-free ambiguity state for the specific satellite in the geometry filter and the value of a widelane ambiguity state for the specific satellite in one of the code-carrier filters.

7. The method of claim 5, wherein determining that a cycle slip has occurred comprises monitoring an ionospheric cycle slip indicator per satellite to identify an ionospheric cycle slip as to a specific satellite, and wherein resetting values of any variables of a set of state variables which are affected by the cycle slip comprises resetting the value of an ionospheric ambiguity state for the specific satellite in one of the ionospheric filters.

8. The method of claim 5, wherein determining that a cycle slip has occurred comprises monitoring a widelane cycle slip indicator per satellite to identify a widelane cycle slip as to a specific satellite, and wherein resetting values of any variables of a set of state variables which are affected by the cycle slip comprises resetting the value of an ionospheric-free ambiguity state for the specific satellite in the geometry filter, resetting the value of a widelane ambiguity state for the specific satellite in one of the code-carrier filters, and resetting the value of an ionospheric ambiguity state for the specific satellite in one of the ionospheric filters.

9. The method of claim 1, wherein using each epoch of rover observations and correction data to estimate updated values for the set of state variables comprises applying a filter.

10. The method of claim 9, wherein determining that a cycle slip has occurred comprises monitoring an ionospheric-free cycle slip indicator per satellite to identify an ionospheric-free cycle slip as to a specific satellite, and wherein resetting values of any variables of a set of state variables which are affected by the cycle slip comprises resetting the value of an ionospheric-free ambiguity state for the specific satellite in the filter.

11. The method of claim 9, wherein determining that a cycle slip has occurred comprises monitoring an ionospheric cycle slip indicator per satellite to identify an ionospheric cycle slip as to a specific satellite, and wherein resetting values of any variables of a set of state variables which are affected by the cycle slip comprises resetting the value of an ionospheric ambiguity state for the specific satellite in the filter.

12. An apparatus for determining a precise position of a rover located within a region using rover observations comprising code observations and carrier-phase observations of GNSS signals on at least two carrier frequencies over multiple epochs and correction data comprising for each of the epochs at least one code bias per satellite, at least one of:

(i) a fixed-nature MW bias per satellite or (ii) values from which a fixed-nature MW bias per satellite is derivable, or at least one of;

(iii) an ionospheric delay per satellite for each of multiple regional network stations, or (iv) non-ionospheric corrections, the apparatus comprising;

a. a synthetic reference station module operative to create synthetic reference data for each of the epochs from the correction data for a synthetic station location;

b. a cycle slip module operative to determine for each epoch whether a cycle slip has occurred in at least one of (i) the rover observations or (ii) observations at network stations used to prepare the correction data;

c. a resetting module operative upon determination that a cycle slip has occurred to reset values of any variables of a set of state variables which are affected by the cycle slip while retaining values of at least some variables of the set which are not affected by the cycle slip; and

d. an estimator module operative to use each epoch of rover observations and correction data to estimate updated values for the set of state variables, the state variables comprising a set of ambiguities and coordinates of a precise rover position.

13. The apparatus of claim 12, wherein the correction data comprises at least one cycle slip indicator, and wherein state variables affected by the cycle slip are determined from the at least one cycle slip indicator.

14. The apparatus of claim 12, wherein the correction data comprises at least one ionospheric-free cycle slip indicator per satellite for a plurality of satellites, wherein the cycle slip module is operative to monitor the ionospheric-free cycle slip indicators to determine an identity of at least one satellite for which an ionospheric-free cycle slip has occurred, and wherein the resetting module is operative to reset values of state variables affected by the ionospheric-free cycle slip.

15. The apparatus of claim 12, wherein the correction data comprises at least one ionospheric cycle slip indicator per satellite per station of a network from which the correction data are derived, wherein the cycle slip module is operative to monitor the ionospheric cycle slip indicators to determine an identity of at least one satellite-station pair for which an ionospheric cycle slip has occurred, and wherein the resetting module is operative to reset state variables affected by the at least one ionospheric cycle slip.

16. The apparatus of claim 12, wherein the estimator comprises a factorized array of recursive filters comprising a code-carrier filter bank using a Melbourne-Wuebbena code-carrier combination, a an ionospheric filter bank using an ionospheric carrier combination, and a geometry filter using an ionospheric-free carrier combination.

17. The apparatus of claim 16, wherein the resetting module is operative upon occurrence of an ionospheric-free cycle slip as to a specific satellite to reset the value of an ionospheric-free ambiguity state for the specific satellite in the geometry filter and the value of a widelane ambiguity state for the specific satellite in one of the code-carrier filters.

18. The apparatus of claim 16, wherein the resetting module is operative upon occurrence of an ionospheric cycle slip as to a specific satellite to reset the value of an ionospheric ambiguity state for the specific satellite in one of the ionospheric filters.

19. The apparatus of claim 16, wherein the resetting module is operative upon occurrence of a widelane cycle slip as to a specific satellite to reset the value of an ionospheric-free ambiguity state for the specific satellite in the geometry filter, reset the value of a widelane ambiguity state for the specific satellite in one of the code-carrier filters, and reset the value of an ionospheric ambiguity state for the specific satellite in one of the ionospheric filters.

20. The apparatus of claim 12, wherein the estimator comprises a filter.

21. The apparatus of claim 20, wherein the resetting module is operative upon occurrence of an ionospheric-free cycle slip as to a specific satellite to reset the value of an ionospheric-free ambiguity state for the specific satellite in the filter.

22. The apparatus of claim 20, wherein the resetting module is operative upon occurrence of an ionospheric cycle slip as to a specific satellite to reset the value of an ionospheric ambiguity state for the specific satellite in the filter.