an assisted global positioning system for tracking a movable object of interest is disclosed . the system comprises a service center for calculating a tag location , a plurality of ground base stations , a plurality of beacons adapted to transmit individual id data , and at least one gps - based smart tag releasably affixed to the movable object . the system components are interconnected by means of one or more communication links . the service center is adapted for inquiring the tag and receiving a response from the tag constituting pseudo - ranges according to a predetermined protocol .