Road map feedback corrections in tightly coupled gps and dead reckoning vehicle navigation

Road map feedback is included in a tightly coupled GPS and dead-reckoning system that collects wheel speed transducer data over a vehicle's network to compute vehicle range and direction. On-board road maps in DVD disks provide a database of road segments that are matched to the current navigation solutions. The dead-reckoning bridges over gaps in navigation solutions that would otherwise occur when GPS signal transmission is lost in tunnels, parking garages, and other common situations. The road map fitting controls drift that would otherwise accumulate during long periods of dead reckoning only operation.