Method and apparatus for automatically tracking the location of vehicles

A system for automatically tracking the location of a vehicle, comprising:

• visual image detecting means mounted on said vehicle for obtaining analog image signals representative of at least a portion of a panoramic view of the surroundings about said vehicle;
• digital signal processing means for converting said analog image signals into a plurality of successive digitized first image data strips as the associated vehicle travels along a route, each of said plurality of first image data strips including information relating to features of scenery about said vehicle at successive locations or landmarks along said route, respectively, whereby when said vehicle retraces travel along at least a portion of said route, said digital signal processing means converts resulting said analog image signals into successive digitized second image data strips corresponding to a unique one of said first image data strips, respectively;
• sparse tracking means for utilizing selected ones of said plurality of first image data strips for establishing a sparse database thereof in memory, the selected image data strips representing substantially spaced apart successive locations along said route, said sparse tracking means further including landmark recognition means for comparing each of said second image data strips as they occur in real time with the ones of said first image data strips of the sparse database, respectively, for locating said vehicle in real time at the landmark or location associated with the one of said first image data strips most closely corresponding to the current said second image data strip;
• dense tracking means for utilizing all of said plurality of first image data strips for establishing a dense database thereof in memory, representing adjacent successive locations along said route, said dense tracking means further including matching means for determining the closest match between each of said second image data strips as they occur in real time and said plurality of first image data strips, respectively, for locating said vehicle in real time at the location associated with the closest matching one of said first image data strips to the current second image data strip, said dense tracking means providing more accurate but less robust tracking of said vehicle than said sparse tracking means;
• and
• switching means responsive in one mode to straying of said vehicle from said route for transferring the tracking of said vehicle from said dense tracking means to said sparse tracking means, and thereafter responsive in another mode to said sparse tracking means recovering the location of said vehicle for at least a predetermined time, for transferring vehicle tracking back to said dense tracking means, and retaining said dense tracking means active as long as said vehicle continues travel on said route in a manner permitting said dense tracking means to locate said vehicle.