System and method for validating GNSS location input
A computer implemented method of validating an output from a GNSS at a receiver including a fusion system comprising location sensors. A location estimate and a location error estimate are computed. A navigation update including a sensor location estimate and sensor location error estimate is also computed with the fusion system based on sensor measurements from the location sensors. A determination is made as to whether or not GNSS filters should be applied based at least on the location estimate, the sensor location estimate, and the sensor location error estimate. When GNSS filters should be applied, the location estimate and/or the location error estimate may be adjusted or rejected and a new navigation update may be computed with the fusion system based on the adjustment or rejection. When the GNSS filters should not be applied, the new navigation update is computed with the location estimate and the location error estimate.
1. A computer implemented method of validating an output from a global navigation satellite system (GNSS), the method comprising:
receiving at a GNSS receiver including a fusion system an output from at least one satellite in the GNSS, the fusion system comprising one or more location sensors;
computing a GNSS location estimate input and a GNSS location error estimate input;
computing a navigation update with the fusion system based on sensor measurements from the one or more location sensors, wherein the navigation update includes a sensor location estimate and a sensor location error estimate;
determining when one or more GNSS filters are applied based at least on the GNSS location estimate input, the sensor location estimate, and the sensor location error estimate;
wherein when the one or more GNSS filters are applied, applying the one or more GNSS filters by adjusting or rejecting one or more of the GNSS location estimate input and the GNSS location error estimate input and computing a new navigation update with the fusion system based on the adjusting or rejecting of the one or more of the GNSS location estimate input and the GNSS location error estimate input; and
wherein when the one or more GNSS filters are not applied, computing the new navigation update with the fusion system based on accepting the GNSS location estimate input and the GNSS location error estimate input.
2. The method of claim 1 , wherein the computing a GNSS location estimate input and GNSS location error estimate input includes initializing the fusion system based on one or more of a good GNSS fix, a user map check-in, and a range to a known location.
3. The method of claim 2 , wherein the initializing the fusion system comprises ensuring that at least one of an attitude estimate, a scale estimate, and a drift estimate for the GNSS receiver are available.
4. The method of claim 1 , further comprising:
receiving at the GNSS receive environmental information based on the GNSS location estimate input and the GNSS location error estimate input, and wherein the adjusting or rejecting the one or more of the GNSS location estimate input and the GNSS location error estimate input is based on the environmental information.
5. The method of claim 4 , wherein the adjusting or rejecting the one or more of the GNSS location estimate input and the GNSS location error estimate input includes one or more of adjusting the GNSS location error estimate input, removing the output from one or more satellites in the output from the GNSS, and rejecting the output from the GNSS.
6. The method of claim 5 , wherein the adjusting the GNSS location error estimate input includes increasing the location error estimate when the location estimate is within a threshold distance from a building.
7. The method of claim 6 , wherein the adjusting the GNSS location error estimate input includes tripling the GNSS location error estimate input when the threshold distance is within 5 feet of the building and doubling the GNSS location error estimate input when the threshold distance is within 20 feet of the building.
8. The method of claim 6 , wherein the adjusting the GNSS location error estimate input includes increasing a radius of the GNSS location error estimate input or increasing the GNSS location error estimate input along a single axis.
9. The method of claim 5 , wherein the removing the output from one or more satellites includes removing the output from a satellite when the satellite is determined to not be in a direct line of sight to the GNSS receiver.
10. The method of claim 9 , wherein the satellite is determined to not be in a direct line of sight based on a height of a building, a distance from the GNSS receiver to the building, and an azimuth and elevation of the satellite relative to the location estimate.
11. The method of claim 4 , wherein the environmental information includes one or more of map data, a building outline, a building height and terrain data.
12. The method of claim 1 , wherein the determining when the one or more GNSS filters are applied includes comparing the sensor location estimate to the GNSS location estimate input and the sensor location error estimate to the GNSS location error estimate input and applying the one or more GNSS filters when the comparison is inconsistent.
13. The method of claim 12 , wherein the comparison is inconsistent when there is little to no overlap between one or more of the sensor location estimate and the GNSS location estimate input and the sensor location error estimate and the GNSS location error estimate input.
14. The method of claim 1 , wherein the determining when the one or more GNSS filters are applied includes:
computing a first movement of the GNSS receiver independent of the output of the GNSS;
computing a second movement of the GNSS receiver dependent on the output of the GNSS;
comparing the first movement to the second movement; and
when the first movement is inconsistent with the second movement rejecting the one or more of the GNSS location estimate input and the GNSS location error estimate input.
15. The method of claim 14 , wherein the first movement is a first velocity and the second movement is a second velocity.
16. The method of claim 14 , wherein the first movement is a first path shape and the second movement is a second path shape.
17. The method of claim 16 , wherein the rejecting the one or more of the GNSS location estimate input and the GNSS location error estimate input includes:
saving the first path shape and the second path shape over a period;
comparing the first path shape to the second path shape; and
recomputing the new navigation update with the fusion system when the first path shape is inconsistent with the second path shape.
18. The method of claim 14 , wherein the first movement is a first distance traveled from a known location and the second movement is a second distance traveled from the known location.
19. The method of claim 1 , wherein the one or more location sensors comprise at least one of an accelerometer, a gyroscope, a barometer, a magnetic sensor, a ranging sensor, and a vision sensor.
20. The method of claim 1 , further comprising:
saving a rejected GNSS location estimate input as a new potential repeater location when the rejected GNSS location estimate input has not been rejected before and saving the rejected GNSS location estimate input as a known repeater location when the rejected GNSS location estimate input has been rejected before, wherein computing the new navigation update is based on remaining measurements.