Vehicle navigation by dead reckoning and GNSS-aided map-matching

1. A vehicle dead reckoning and GNSS-aided map-matching navigation system comprising:

a map-match navigation module in a handheld device, the module configured to:

send map-match feedback messages to an estimator via a port, the map-match feedback messages including a position, a heading, a position variance and a heading variance of a vehicle estimated based on at least one of a road width, an average road heading, a length of a snap distance, or road choice probabilities, the port enforcing a map-match feedback message format and protocol for communication between the map-match navigation module and the estimator;

receive vehicle state estimates from the estimator, the estimator including a recursive Bayesian filter that computes an estimated position and an estimated heading of the vehicle based on: GNSS position estimates, estimates of the vehicle's speed from a speed sensor, inertial navigation estimates from inertial sensors, and the map-match feedback messages received via the port including the position variance and the heading variance, wherein the vehicle state estimates include the estimated position and the estimated heading of the vehicle, and the estimates of the vehicle's speed;

receive map updates;

accumulate a recent history of changes of the vehicle's speed and heading based on the estimates of the vehicle's speed and the estimated heading of the vehicle;

estimate an updated position and an updated heading of the vehicle based on the estimated position and the estimated heading of the vehicle, the recent history of the changes of the vehicle's speed and heading, and map data; and

send the updated position and the updated heading of the vehicle to a user interface device.

2. The system of claim 1 , the estimator being mounted in the vehicle.

3. The system of claim 1 , the estimator being included in the handheld device.

4. The system of claim 1 , the map-match navigation module further configured to receive the estimates of the vehicle's speed from the speed sensor.

5. The system of claim 4 , the speed sensor being mounted in the vehicle.

6. The system of claim 1 , the map-match navigation module further configured to receive inertial navigation estimates from the inertial sensors.

7. The system of claim 6 , the inertial sensors being mounted in the vehicle.

8. The system of claim 1 , the map-match navigation module further configured to accumulate a track of the vehicle's recent positions.

9. The system of claim 8 , the map-match navigation module further configured to fit the track to the map data to estimate the vehicle's position.

10. The system of claim 1 , the map-match feedback messages further including the snap distance from the position of the vehicle to a nearest road.

11. The system of claim 1 , the map-match feedback messages further including Boolean flags to indicate when the vehicle is in a tunnel or not on a road.

12. The system of claim 1 , the estimator updating sensor bias estimates based on information in the map-match feedback messages.

13. A vehicle dead reckoning and GNSS-aided map-matching navigation method comprising, using a map-match navigation module in a handheld device:

sending map-match feedback messages to an estimator via a port, the map-match feedback messages including a position, a heading, a position variance and a heading variance of a vehicle estimated based on at least one of a road width, an average road heading, a length of a snap distance, or road choice probabilities, the port enforcing a map-match feedback message format and protocol for communication between the map-match navigation module and the estimator;

receiving vehicle state estimates from the estimator, the estimator including a recursive Bayesian filter that computes an estimated position and an estimated heading of the vehicle based on: GNSS position estimates, estimates of the vehicle's speed from a speed sensor, inertial navigation estimates from inertial sensors, and the map-match feedback messages received via the port including the position variance and the heading variance, wherein the vehicle state estimates include the estimated position and the estimated heading of the vehicle, and the estimates of the vehicle's speed;

receiving map updates;

accumulating a recent history of changes in the vehicle's speed and heading based on the estimates of the vehicle's speed and the estimated heading of the vehicle;

estimating an updated position and an updated heading of the vehicle based on the estimated position and the estimated heading of the vehicle, the recent history of the changes in the vehicle's speed and heading, and map data; and

sending the updated position and the updated heading of the vehicle to a user interface device.

14. The method of claim 13 , the estimator being mounted in the vehicle.

15. The method of claim 13 , the estimator being included in the handheld device.

16. The method of claim 13 , further comprising receiving the estimates of the vehicle's speed from the speed sensor.

17. The method of claim 16 , the speed sensor being mounted in the vehicle.

18. The method of claim 13 , further comprising receiving the inertial navigation estimates from the inertial sensors.

19. The method of claim 18 , the inertial sensors being mounted in the vehicle.

20. The method of claim 13 , further comprising accumulating a track of the vehicle's recent positions.

21. The method of claim 20 , further comprising fitting the track to the map data to estimate the vehicle's position.

22. The method of claim 13 , the map-match feedback messages further including the snap distance from the position of the vehicle to a nearest road.

23. The method of claim 13 , the map-match feedback messages further including Boolean flags to indicate when the vehicle is in a tunnel or not on a road.

24. The method of claim 13 , the estimator updating sensor bias estimates based on information in the map-match feedback messages.