System and method for computing positioning protection levels
A method or system can include or be configured to receive a set of satellite observations, receiving sensor data, determining a position estimate and associated positioning error for a rover based on the set of satellite observations and the sensor data, determine a protection level associated with the position estimate based on a set of potential faults, and optionally provide an alert when the positioning error exceeds the protection level.
1. A system comprising a processor configured to:
determine a delayed positioning solution for a rover comprising:
receiving satellite observations tracked by an antenna mounted to a rover; and
determining the delayed positioning solution by:
determining a set of carrier phase ambiguity hypothesis for each satellite observation of the satellite observations; and
selecting a carrier phase ambiguity of the set of carrier phase ambiguity hypotheses based on results of a hypothesis test comparing carrier phase ambiguities of the set of integer phase ambiguity hypotheses; and
calculating the delayed positioning solution and a delayed positioning solution covariance using the satellite observations and the selected carrier phase ambiguities; and
determine a real-time positioning solution for the rover by:
receiving sensor data measured by an inertial measurement unit of the rover;
correcting the sensor data for a sensor bias determined based on the delayed positioning solution;
propagating a previous real-time positioning solution to the real-time positioning solution based on the corrected sensor data; and
propagating the delayed positioning solution covariance.
2. The system of claim 1 , wherein the delayed positioning solution is delayed by at most 1 second relative to the real-time positioning solution.
3. The system of claim 1 , wherein determining the real-time positioning solution for the rover further comprises determining a protection level associated with the real-time positioning solution.
4. The system of claim 3 , where the protection level is determined based on a set of potential faults comprising potential satellite faults and potential sensor faults.
5. The system of claim 4 , wherein the potential satellite faults comprise multipath events, interference errors, cycle slips, data corruption, code carrier incoherency, satellite clock faults, satellite clock drift, unscheduled satellite maneuvers, jump drift, antenna pattern changing, non-line of sight faults, receiver clock offset jumps, evil waveform, or combinations thereof.
6. The system of claim 4 , wherein the potential sensor faults comprise sensor bias instabilities, scale factor errors, clipping problems, update failures, accelerometer error, gyroscope error, signal jamming, signal spoofing, misalignment errors, cross axis errors, thermal gradient errors, acceleration errors, coning errors, sculling errors, centrifugal acceleration effects, or combinations thereof.
7. The system of claim 3 , wherein determining the protection
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where TIR is a target integrity risk, N is a number of events, P(E>PL|H i ) is the impact of event i, PL is the protection level, P(H i ) is the probability of event i occurring, P md (H i ) is the probability of not detecting event i.
8. The system of claim 7 , wherein solving
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comprises iteratively solving
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with a different test protection level for each iteration.
9. The system of claim 3 , wherein the processor is further configured to generate an alert when the protection level exceeds an alert limit.
10. The system of claim 3 , wherein when the satellite observations are not available the protection level is determined using the sensor data.
11. The system of claim 1 , wherein propagating the delayed positioning solution covariances comprises modelling the delayed positioning solution covariances as a Gauss Markov process.
12. The system of claim 11 , wherein a correlation time of the Gauss Markov process depends on a velocity of the rover.
13. The system of claim 1 , wherein the processor is further configured to monitor the satellite observations and the sensor data for a predetermined event, wherein a probability of the predetermined event impacting the data monitoring is independent of a probability of missing detection of the predetermined event.
14. A system comprising a processor configured to:
receive a set of input data comprising satellite observations tracked by an antenna mounted to a rover and sensor data measured by an inertial measurement unit of the rover;
determine a kinematic solution of the rover based on the at least one or satellite observations or sensor data; and
determine a protection level by iteratively solving
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wherein TIR is a target integrity risk, N is a number of events in a list of events, P(E>PL|H i ) is an impact of event i, PL is the protection level, P(H i ) is the probability of event i occurring, P md (H i ) is the probability of not detecting event i.
15. The system of claim 14 , wherein when the protection level exceeds an alert limit, the processor is configured to issue an alarm indicating the protection level exceeding the alert limit.
16. The system of claim 14 , wherein the processor is configured to determine the protection level during a satellite observations outage.
17. The system of claim 14 , wherein during each iteration solving
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comprises solving
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with a different test protection level.
18. The system of claim 14 , wherein the target integrity risk comprises a total integrity risk and an integrity risk for not monitored events.
19. The system of claim 14 , wherein the list of events comprises a set of potential satellite faults, an impact of each satellite fault of the set of potential satellite faults, a probability of each satellite fault of the set of potential satellite faults occurring, a probability of not detecting each satellite fault of the set of potential satellite faults, a set of potential sensor faults, an impact of each sensor fault of the set of potential sensor faults, a probability of each sensor fault of the set of potential sensor faults occurring, and a probability of not detecting each sensor fault of the set of potential sensor faults.
20. The system of claim 19 , where the impact of each satellite fault of the set of potential satellite faults or the impact of each sensor fault of the set of potential sensor faults depends on a magnitude of the respective satellite fault or sensor fault.