Systems and methods for high-integrity satellite positioning

1. A method for determining a position of a global navigation satellite system (GNSS) receiver, the method comprising:

receiving a set of satellite observations from a set of global navigation satellites;

resolving a carrier phase ambiguity for the set of satellite observations;

validating the carrier phase ambiguity using a multistep validation process;

detecting a predetermined event;

in response to detecting the predetermined event, mitigating an effect of the detected predetermined event; and

estimating a position of the GNSS receiver based on the validated carrier phase ambiguity, wherein an integrity risk and a protection level of the estimated position depend on a step of the multistep validation process is used to validate the carrier phase ambiguity.

2. The method of claim 1 , further comprising:

generating a set of GNSS corrections based on a set of satellite observations recorded at a first set of reference stations; and

validating the GNSS corrections against a second set of satellite observations recorded at a second set of reference stations.

3. The method of claim 2 , wherein the first and second set of reference stations are distinct.

4. The method of claim 1 , wherein the integrity risk is at most 10 −7 /hour.

5. The method of claim 1 , wherein the predetermined event corresponds to at least one of: code carrier incoherency, satellite clock step error, satellite clock drift greater than 1 cm/s, pseudorange multipath, carrier phase multipath, carrier phase cycle slip, non-line of sight tracking, false acquisition, Galileo binary offset carrier second peak tracking, and spoofing.

6. The method of claim 1 , wherein the multistep validation process comprises a first validation step, wherein the carrier phase ambiguities are validated simultaneously.

7. The method of claim 6 , wherein the multistep validation process comprises a second validation step comprising validating an integer carrier phase ambiguity of satellite observations associated with a first satellite constellation and an integer carrier phase ambiguity of satellite observations associated with a second satellite constellation.

8. The method of claim 1 , further comprising estimating a velocity of the GNSS receiver using time-differenced carrier phase measurements.

9. The method of claim 1 , further comprising determining a risk for the carrier phase ambiguity resolution, wherein the risk corresponds to an upper bound on a probability for an incorrect carrier phase ambiguity resolution.

10. The method of claim 9 , wherein a maximum risk for the carrier phase ambiguity resolution is determined using a Monte Carlo simulation.

11. A method for determining a position of a global navigation satellite system (GNSS) receiver, the method comprising:

receiving a first set of reference station observations associated with a first set of reference stations;

monitoring the first set of reference station observations for a predetermined event;

in response to detecting the predetermined event, generating a predetermined event mitigated set of reference station observations by mitigating an effect of the detected predetermined event in the first set of reference station observations;

determining corrections based on the predetermined event mitigated set of reference station observations;

validating the corrections using a second set of reference station observations associated with a second set of reference stations;

receiving a set of satellite observations from a set of global navigation satellites;

resolving a carrier phase ambiguity for the set of satellite observations based in part on the validated corrections; and

estimating a position of the GNSS receiver based on the carrier phase ambiguity.

12. The method of claim 11 , wherein the estimated position comprises an integrity risk of at most 10 −4 per hour.

13. The method of claim 11 , wherein the predetermined event corresponds to at least one of environmental feared events, network feared events, satellite clock drift of at most 1 cm/s, issue of data anomaly, erroneous broadcast ephemeris, constellation failure, reference station multipath, and reference station cycle slip.

14. The method of claim 11 , wherein validating the corrections comprises:

correcting the second set of reference station observations using the corrections;

determining residuals for the set of corrected satellite observations; and

validating the corrections when the residuals are below a correction validation threshold.

15. The method of claim 11 , wherein determining the corrections comprises generating a model by:

estimating a delay associated with each reference station of the first set of reference stations using a filter; and

interpolating between the delays associated with each reference station to generate the atmospheric model.

16. The method of claim 15 , wherein the filter comprises a precise point positioning filter.

17. The method of claim 11 , wherein resolving the carrier phase ambiguity comprises validating an integer carrier phase ambiguity of satellite observations associated with a first satellite constellation and an integer carrier phase ambiguity of satellite observations associated with a second satellite constellation.

18. The method of claim 17 :

wherein validating the integer carrier phase ambiguity of satellite observations associated with the first satellite constellation comprises applying the corrections directly; and

validating the integer carrier phase ambiguity of satellite observations associated with the second satellite constellation comprises applying the corrections with a residual regional offset.

19. The method of claim 18 , wherein the residual regional offset is estimated based on applying the corrections to the second set of reference station observations.

20. The method of claim 11 , wherein monitoring the first set of reference station observations for the predetermined event comprises monitoring the first set of reference station observations for an outlier using one of a scaled residual technique, a variance threshold technique, and a hybrid technique.