Abstract: A location tracking system for tracking the location of items within a controlled area comprises a plurality of RFID tags located according to the required accuracy of the location determinations. Vehicles configured to transport items being tracked include two RFID interrogators configured to acquire RFID information from the plurality of RFID tags and to transmit the RFID tag information to a location authority. The separation the two RFID interrogators is set based on the spacing of the plurality of RFID tags such that the required accuracy results. The location authority can then simply map the RFID tag information to coordinate information stored for each of the plurality of tags to obtain the location of the vehicle and, therefore, the item being transported.

Abstract: A system comprised of a parent and child unit perform multiple position-dependent functions. The parent and child unit each comprises a directional antenna, power source, transceiver, processor and memory. The processor is coupled to the transceiver to control transmission and reception in each unit according to a predetermined stored protocol. The parent unit has a directional antenna and the child unit has an omnidirectional antenna. The transceivers in the units bidirectionally communicate to automatically perform one or more of the multiple position-dependent functions including electronic leash, finder, and proximity functions. Typically, a plurality of child units bidirectionally communicate with the parent unit to automatically perform the multiple position-dependent functions over a plurality of frequencies, by means of a plurality of different digital codes or both. The invention also comprises a method comprised of the steps necessary for performing the functions.