System and method for position fix estimation using two or more antennas
A dual-antenna positioning system includes a first GNSS antenna/receiver, a second GNSS antenna/receiver, and a GNSS processor system. The first GNSS antenna/receiver is located at a first position and calculates a first pseudo-range based on a received GNSS signal. The second GNSS antenna/receiver is located at a second position a known distance from the first GNSS antenna/receiver, wherein the second GNSS antenna/receiver calculates a second pseudo-range based on a received GNSS signal. The GNSS processor system configured to receive the first pseudo-range and the second pseudo-range, wherein in response to the GNSS processor system identifying one of the first and second pseudo-ranges as erroneous and one of the first and second pseudo-ranges as valid, the GNSS processing system calculates a corrected pseudo-range and utilizes the corrected pseudo-range and the valid pseudo-range to determine GNSS position fix estimates for the first GNSS antenna/receiver and the second GNSS antenna/receiver.
1. A dual-antenna positioning system comprising:
a first global navigation satellite system (GNSS) antenna/receiver located at a first position, wherein the first GNSS antenna/receiver calculates a first pseudo-range based on a received GNSS signal;
a second GNSS antenna/receiver located at a second position a known distance from the first GNSS antenna/receiver, wherein the second GNSS antenna/receiver calculates a second pseudo-range based on a received GNSS signal; and
a GNSS processor system configured to receive the first pseudo-range and the second pseudo-range, wherein in response to the processor system identifying one of the first and second pseudo-ranges as erroneous and one of the first and second pseudo-ranges as valid, the processing system calculates a corrected pseudo-range and utilizes the corrected pseudo-range and the valid pseudo-range to determine GNSS position fix estimates for the first GNSS antenna/receiver and the second GNSS antenna/receiver, wherein the GNSS processing system calculates the corrected pseudo-range based on valid pseudo-range, the known distance between the first GNSS antenna/receiver and the second GNSS antenna/receiver, and an angle of arrival (AoA) of the received GNSS signal at the GNSS antenna/receiver that generated the valid pseudo-range.
2. The dual-antenna positioning system of claim 1 , wherein the GNSS processing system calculates AoA of the received GNSS signal based on a current position/orientation estimate of the dual-antenna positioning system and GNSS satellite position.
3. The dual-antenna positioning system of claim 2 , wherein the current position/orientation estimate is based on a previous GNSS position/orientation fix estimate and known speed and direction of the dual-antenna positioning system.
4. The dual-antenna positioning system of claim 2 , further including:
an inertial measurement unit (IMU), wherein the GNSS processing system utilizes IMU data received from the IMU in combination with previous GNSS position/orientation fix estimates to generate the current position/orientation estimate.
5. A method of determining a global navigation satellite system (GNSS) position fix estimate, the method comprising:
receiving a first pseudo-range from a first GNSS antenna/receiver;
receiving a second pseudo-range from a second GNSS antenna/receiver located a known distance from the first GNSS antenna/receiver;
determining that the first pseudo-range is erroneous;
determining that the second pseudo-range is valid;
calculating a corrected first pseudo-range based on the second pseudo-range, the known distance between the first GNSS antenna/receiver and the second GNSS antenna/receiver, and angle-of-arrival (AoA) of a GNSS signal received at the second GNSS antenna/receiver; and
calculating a GNSS position fix estimate for the first GNSS antenna/receiver based, at least in part, on the corrected first pseudo-range.
6. The method of claim 5 , wherein determining that the first pseudo-range is erroneous includes comparing the first pseudo-range to an expected pseudo-range, wherein the first pseudo-range is determined to be erroneous if it exceeds the expected pseudo-range by a threshold amount.
7. The method of claim 6 , wherein the expected pseudo-range is calculated based on an IMU-based position estimate generated based on a previous GNSS position fix estimate and inertial measurement unit (IMU) data provided by an IMU.
8. The method of claim 6 , wherein the expected pseudo-range is calculated based on a wheel tick input utilized to determine a distance traveled from a previous GNSS position fix estimate.
9. The method of claim 5 , wherein determining that the second pseudo-range is valid includes comparing the second pseudo-range to an expected pseudo-range, wherein the second pseudo-range is determined to be valid if it is within a threshold of the expected pseudo-range.
10. The method of claim 5 , wherein the AoA of the GNSS signal is determined based on a known position of a GNSS satellite that originated the GNSS signal and a position/orientation estimate of the second antenna/receiver.
11. The method of claim 10 , wherein the position/orientation estimate of the second antenna/receiver is based on a previous GNSS position/orientation fix estimate and inertial measurement unit (IMU) data.
12. The method of claim 5 , wherein the calculating the corrected first pseudo-range is based on the following equation:
R 2′=√{square root over ( R 1 2 +d 2 −2( d*R 1*cos(AoA)))}
wherein R 1 is the second pseudo-range, d is the distance between the first GNSS antenna/receiver and the second GNSS antenna/receiver, AoA is the angle-of-arrival of the GNSS signal received at the second GNSS antenna/receiver and R 2 ′ is the corrected pseudo-range.
13. A global-navigation satellite system (GNSS) configured to receive GNSS data from a first GNSS antenna/receiver and a second GNSS antenna/receiver and to provide in response a GNSS position/orientation estimate for the first GNSS antenna/receiver and the second GNSS antenna/receiver, the GNSS system including a processor and a computer readable medium that stores instructions that, when executed by the processor, perform the following method:
identifying a first pseudo-range associated with the first GNSS antenna/receiver as erroneous;
identifying a second pseudo-range associated with the second GNSS antenna/receiver as valid;
calculating a corrected first pseudo-range based on the second pseudo-range, the known distance between the first GNSS antenna/receiver and the second GNSS antenna/receiver and angle-of-arrival (AoA) of the GNSS signal received at the second GNSS antenna/receiver; and
calculating a GNSS position fix estimate for the first GNSS antenna/receiver based, at least in part, on the corrected first pseudo-range.
14. The GNSS of claim 13 , wherein identifying that the first pseudo-range is erroneous includes comparing the first pseudo-range to an expected pseudo-range, wherein the first pseudo-range is determined to be erroneous if it differs from the expected pseudo-range by a threshold amount.
15. The GNSS of claim 14 , wherein the expected pseudo-range is calculated based on an IMU-based position estimate generated based on a previous GNSS position fix estimate and inertial measurement unit (IMU) data provided by an IMU.
16. The GNSS of claim 14 , wherein the expected pseudo-range is calculated based on a wheel tick-based position estimate generated based on a previous GNSS position fix estimate and a wheel tick input defining a distance traveled by the vehicle since the previous GNSS position fix estimate.
17. The GNSS of claim 13 , wherein the AoA of the GNSS signal is determined based on a known position of a GNSS satellite that originated the GNSS signal and a position/orientation estimate of the second antenna/receiver.
18. The GNSS of claim 17 , wherein the position/orientation estimate of the second antenna/receiver is based on a previous GNSS position/orientation fix estimate and inertial measurement unit (IMU) data received by the GNSS from an IMU.
19. The GNSS of claim 13 , wherein the calculating the corrected first pseudo-range is based on the following equation:
R 2′=√{square root over ( R 1 2 +d 2 −2( d*R 1*cos(AoA)))}
wherein R 1 is the second pseudo-range, d is the distance between the first GNSS antenna/receiver and the second GNSS antenna/receiver, AoA is the angle-of-arrival of the GNSS signal received at the second GNSS antenna/receiver and R 2 ′ is the corrected pseudo-range.