System and method for reconverging GNSS position estimates
A system and method for determining a receiver position can include determining a receiver position based on a set of satellite observations, determining the receiver position based on sensor measurements, determining a satellite observation discontinuity; based on the satellite observation discontinuity, determining a second receiver position.
1. A method for determining a receiver position after a phase lock loss event, comprising:
before the phase lock loss event, determining a first high integrity receiver position based on a first set of satellite observations;
during a phase lock loss period following the phase lock loss event, determining the receiver position based on IMU measurements;
after the phase lock loss period, determining a cycle slip between the first set of satellite observations and a second set of satellite observations measured after the phase lock loss period based on:
the receiver position determined based on the IMU measurements during the phase lock loss period; and
the first high integrity receiver position prior to the phase lock loss event; and
when a standard deviation of the cycle slip is less than a standard deviation threshold, determining a second high integrity receiver position using the cycle slip
wherein determining the cycle slip comprises:
estimating a current carrier phase using the receiver position determined based on the IMU measurements and the first high integrity receiver position;
determining a residual between the estimated carrier phase and the second set of satellite observations; and
determining an integer nearest to the residual, wherein the integer is the cycle slip.
2. The method of claim 1 , wherein the first high integrity receiver position comprises an integrity risk of at most 10 −7 per hour and a protection level that is at most 3 m.
3. The method of claim 1 , wherein the second high integrity receiver position comprises an integrity risk of at most 10 −4 per hour and a protection level that is at most 1 m.
4. The method of claim 1 , wherein the second high integrity receiver position comprises an integrity risk of at most 10 −7 per hour and a protection level that is at most 3 m.
5. The method of claim 1 , wherein determining the first high integrity receiver position comprises:
receiving the first set of satellite observations from a set of global navigation satellites;
resolving a carrier phase ambiguity for the first set of satellite observations;
validating the carrier phase ambiguity using a multistep validation process;
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 which step of the multistep validation process is used to validate the carrier phase ambiguity.
6. The method of claim 5 , further comprising: receiving validated corrections from an external server, wherein the carrier phase ambiguity is resolved based on the validated corrections.
7. The method of claim 1 , wherein determining the second high integrity receiver position comprises determining the second high integrity receiver position without resolving the carrier phase ambiguity.
8. The method of claim 1 , wherein the cycle slip is determined without tightly coupling the first set of satellite observations and the IMU measurements.
9. The method of claim 1 , wherein the standard deviation threshold is at most ⅓ of a cycle.
10. The method of claim 1 , wherein the phase lock loss duration is at most 10 seconds.
11. A method for determining a receiver position after a phase lock loss event, comprising:
before the phase lock loss event, determining a first high integrity receiver position based on a first set of satellite observations comprising:
receiving the first set of satellite observations from a set of global navigation satellites;
resolving a carrier phase ambiguity for the first set of satellite observations;
validating the carrier phase ambiguity using a multistep validation process;
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 which step of the multistep validation process is used to validate the carrier phase ambiguity,
during a phase lock loss period following the phase lock loss event, determining the receiver position based on IMU measurements;
after the phase lock loss period, determining a cycle slip between the first set of satellite observations and a second set of satellite observations measured after the phase lock loss period based on:
the receiver position determined based on the IMU measurements during the phase lock loss period; and
the first high integrity receiver position prior to the phase lock loss event; and
when a standard deviation of the cycle slip is less than a standard deviation threshold, determining a second high integrity receiver position using the cycle slip.
12. The method of claim 11 , further comprising: receiving validated corrections from an external server, wherein the carrier phase ambiguity is resolved based on the validated corrections.