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

1. A vehicle navigation system comprising:

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

send map-match feedback messages to an estimator, the map-match feedback messages including a position, a heading, a position variance, and a heading variance of a vehicle, a most-likely road the vehicle is traveling on, and a probability of the most-likely road being correct;

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 including the position variance, the heading variance, the most-likely road the vehicle is traveling on, and the probability of the most-likely road being correct, 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 updates of map data;

estimate an updated position and an updated heading of the vehicle based on the estimated position and the estimated heading of the vehicle, and the updated map data; and

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

2. The vehicle navigation system of claim 1 , wherein the estimator is mounted in the vehicle.

3. The vehicle navigation system of claim 1 , wherein the estimator is included in the handheld device.

4. The vehicle navigation system of claim 1 , wherein the map-match feedback messages further include a snap distance from the position of the vehicle to the most-likely road.

5. The vehicle navigation system of claim 4 , wherein the position variance and the heading variance of the vehicle are estimated based on at least one of a road width, an average road heading, a length of the snap distance, or the probability of the most-likely road being correct.

6. The vehicle navigation system of claim 1 , wherein the map-match navigation module is further configured to receive vehicle speed estimates from the speed sensor.

7. The vehicle navigation system of claim 6 , wherein the speed sensor is mounted in the vehicle.

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

9. The vehicle navigation system of claim 8 , wherein the inertial sensors are mounted in the vehicle.

10. The vehicle navigation system of claim 1 , wherein the map-match navigation module is further configured to accumulate a recent history of changes of the vehicle's speed and heading based on the estimated position and the estimated heading of the vehicle.

11. The vehicle navigation system of claim 10 , wherein the map-match navigation module is further configured to fit the recent history of the changes of the vehicle's speed and heading to the map data to estimate the updated position of the vehicle.

12. A vehicle navigation method comprising, using a map-match navigation module in a handheld device:

sending map-match feedback messages to an estimator, the map-match feedback messages including a position, a heading, a position variance, and a heading variance of a vehicle, a most-likely road the vehicle is traveling on, and a probability of the most-likely road being correct;

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 including the position variance, the heading variance, the most-likely road the vehicle is traveling on, and the probability of the most-likely road being correct, 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 updates of map data;

estimating an updated position and an updated heading of the vehicle based on the estimated position and the estimated heading of the vehicle, and the updated map data; and

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

13. The method of claim 12 , wherein the estimator is mounted in the vehicle.

14. The method of claim 12 , wherein the estimator is included in the handheld device.

15. The method of claim 12 , wherein the map-match feedback messages further include a snap distance from the position of the vehicle to the most-likely road.

16. The method of claim 15 , wherein the position variance and the heading variance of the vehicle are estimated based on at least one of a road width, an average road heading, a length of the snap distance, or the probability of the most-likely road being correct.

17. The method of claim 12 , wherein the map-match navigation module is further configured to accumulate a recent history of changes of the vehicle's speed and heading based on the estimated position and the estimated heading of the vehicle.

18. The method of claim 17 , wherein the map-match navigation module is further configured to fit the recent history of the changes of the vehicle's speed and heading to the map data to estimate the updated position of the vehicle.

19. The method of claim 12 , wherein the map-match feedback messages further include Boolean flags to indicate whether the vehicle is in a tunnel or not on a road.

20. The method of claim 12 , wherein the estimator is configured to update sensor bias estimates based on information in the map-match feedback messages.