System and method for GNSS reflective surface mapping and position fix estimation

1. A system for calculating position estimates, the system comprising:

a GNSS antenna/receiver configured to receive GNSS signals from a plurality of satellites and to calculate a pseudo-range for each received GNSS signal, wherein GNSS signals include both line-of-sight GNSS signals and reflected GNSS signals, wherein the line-of-sight GNSS signals result in accurate pseudo-range calculations and wherein reflected GNSS signals result in erroneous pseudo-range calculations;

a processor system that includes a processor, a satellite location database, and a 3D reflective surface map of a surrounding area, wherein the processor system compares each calculated pseudo-range to an expected pseudo-range for a respective GNSS signal and identifies the calculated pseudo-range as accurate or erroneous based on a difference between the calculated pseudo-range and the expected pseudo-range, wherein the processing system utilizes the 3D reflective surface map, the current position estimate, and satellite location retrieved from the satellite location database to correct the pseudo-ranges identified as erroneous, wherein the processor system calculates an updated position estimate based on the pseudo-ranges collected from LOS GNSS signals and corrected pseudo-ranges corrected by the processing system.

2. The system of claim 1 , wherein the 3D reflective surface map is sub-divided into a plurality of individual regions, wherein each individual region is assigned a refractive index.

3. The system of claim 2 , wherein the processor system calculates the individual region intersected by the reflected GNSS signal based on the current position estimate, the 3D reflective surface map, and the known location of the satellite.

4. The system of claim 1 , wherein the processor system further receives outputs from an inertial measurement unit (IMU), wherein the processor system augments the current position estimate with outputs from the IMU to provide a dead reckoning position estimate, wherein the processor system detects a positional variance between pseudo ranges associated with reflected GNSS signals and expected pseudo-ranges calculated based on the dead reckoning position estimate, wherein the processor system corrects the updated position estimate based on the detected positional variance and angle of arrival (AoA) of the reflected GNSS signals.

5. The system of claim 4 , wherein the positional variance is calculated based on the equation:

Detected Positional Variance=sin(α)*(½)ΔPseudorange

wherein α is the angle of arrival (AoA) and ΔPseudorange is difference between the received pseudo-range and the expected pseudo-range.

6. The system of claim 1 , wherein the expected pseudo-range is calculated based on a current position estimate and/or a predicted position estimate of the GNSS antenna/receiver.

7. The system of claim 6 , wherein the predicted position estimate is calculated based on the current position and motion information associated with the GNSS antenna/receiver.

8. A system for calculating position estimates, the system comprising:

a GNSS antenna/receiver configured to receive GNSS signals from a plurality of satellites and to calculate a pseudo-range for each received GNSS signal, wherein GNSS signals include both line-of-sight GNSS signals and reflected GNSS signals;

a processor system that includes a processor, a satellite location database, and a 3D reflective surface map of a surrounding area, wherein the processor system detects erroneous pseudo-ranges calculated from reflected GNSS signals based on a current position estimate and corrects erroneous pseudo-ranges based on the 3D reflective surface map, the current position estimate, and satellite location retrieved from the satellite location database, wherein the processor system calculates an updated position estimate based on the pseudo-ranges collected from LOS GNSS signals and corrected pseudo-ranges, wherein the 3D reflective surface map is sub-divided into a plurality of individual regions, wherein each individual region is assigned a refractive index, wherein the processor system calculates the individual region intersected by the reflected GNSS signal based on the current position estimate, the 3D reflective surface map, and the known location of the satellite, wherein the processor system calculates a confidence level associated with the corrected pseudo-range calculated for a reflected GNSS signal based at least in part on the refractive index assigned the individual region intersected by the reflected GNSS signal.

9. A method of processing global navigation satellite system (GNSS) signals received from a plurality of GNSS satellites to determine position, the method comprising:

calculating for each GNSS signal received a pseudo-range that estimates a distance between a local antenna and the GNSS satellite that generated the GNSS signal;

comparing the calculated pseudo-range for each GNSS signal to an expected pseudo-range for that GNSS signal, wherein the expected pseudo-range is generated based on a current position estimate or a predicted position estimate;

detecting one or more erroneous pseudo ranges from the calculated pseudo-ranges based at least in part on comparisons of each calculated pseudo-ranges with the expected pseudo-range;

determining, based on information regarding a location of the GNSS satellite that generated the GNSS signal related to the erroneous pseudo range, the current position estimate, and a 3D reflective surface map of surrounding 3D objects, a surface that reflected the GNSS signal;

correcting the erroneous pseudo range based on the location of the GNSS satellite, the location of the surface that reflected the GNSS signal, and the current position estimate; and

generating an updated position estimate based on the calculated pseudo-ranges and the corrected pseudo-ranges.

10. The method of claim 9 , wherein detecting erroneous pseudo-ranges includes comparing the calculated pseudo-range with previously calculated pseudo-ranges to detect large changes indicative of a change in status from a line-of-sight signal to a reflected signal.

11. The method of claim 9 , wherein the 3D reflective surface map further includes a refractive index assigned to each mapped surface.

12. The method of claim 9 , further including:

augmenting the current position estimate with outputs from an inertial measurement unit (IMU) to provide a dead reckoning position estimate;

detecting a difference between the received pseudo-range and the expected pseudo-range based on the dead reckoning position estimate;

calculating a positional variance based on the detected difference between the received pseudo-range and the expected pseudo-range and based on the angle of arrival (AoA); and

correcting the positional variance by adjusting the current position estimate.

13. The method of claim 12 , wherein the positional variance is compared with a threshold value, and wherein the positional variance is corrected in response to the positional variance being greater than the threshold value.

14. The method of claim 12 , wherein the positional variance is calculated based on the equation:

Detected Positional Variance=sin(α)*(½)ΔPseudorange

wherein α is the angle of arrival (AoA) and ΔPseudorange is difference between the received pseudo-range and the expected pseudo-range.

15. A method of processing global navigation satellite system (GNSS) signals received from a plurality of GNSS satellites to determine position, the method comprising:

calculating for each GNSS signal received a pseudo-range that estimates a distance between a local antenna and the GNSS satellite that generated the GNSS signal;

detecting an erroneous pseudo range caused by a reflection of the GNSS signal based at least in part on comparisons of each calculated pseudo-ranges with a current position estimate;

determining, based on information regarding a location of the GNSS satellite that generated the GNSS signal, a current position estimate, and a 3D reflective surface map of surrounding 3D objects, a surface that reflected the GNSS signal;

correcting the erroneous pseudo range based on the location of the GNSS satellite, the location of the surface that reflected the GNSS signal, and the current position estimate; and

generating an updated position estimate based on the calculated pseudo-ranges and the corrected pseudo-ranges, wherein the 3D reflective surface map further includes a refractive index assigned to each mapped surface, and wherein correcting the erroneous pseudo range includes generating a confidence coefficient based on the refractive index assigned to the surface that reflected the GNSS signal.

16. The method of claim 15 , wherein a higher refractive index indicates a more reflective surface and is assigned a higher confidence coefficient.