NAVIGATION SYSTEM FOR A VEHICLE WITH ROUTE RECALCULATION BETWEEN MULTIPLE LOCATIONS

A vehicle navigation system guides a driver along an optimal route from a starting point to a destination, either of which can be specified in categorical terms. That is, the starting point need not be on a road, and the categorical destination can be entered as "nearest gas station" or "closest hardware store." The system selects a number of possible destinations that conform to the driver's specifications and computes, simultaneously for each particular area on a digitally-stored map, possible optimal routes from the vehicle's current position to each possible destination. The optimal route is selected according to conditions of shortest distance, fastest time, or fewest turns set individually or in any combination by the driver, who is guided along the optimal route by messages on a display. A similar procedure, in which a plurality of possible starting points is proposed, yields the optimal route to a destination from an indefinitely specified starting point. A weighting equation gives a priority within a particular map area to each possible optimal route. Thus the navigation system of the present invention finds most efficiently a desired destination on an optimal route from the vehicle's current position or from a starting point from which the vehicle's current position may be reached.