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

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.