Patent ID: 6493649
Filing Date: 2002-12-10
Classification: G01S

Abstract:
A system which enables the position of each of a plurality of labelled objects in a specified environment to be determined by determining the transit time of slowly propagating energy transmitted from a transmitter of slowly propagating energy on each labelled object to a plurality of receivers positioned at fixed points in or around the specified environment, and computing therefrom the actual distance of the transmitter from the receivers, wherein the transmission of the slowly propagating energy is initiated by a burst of high speed propagating energy from a master transmitter of high speed propagating energy located so as to cause transmitted bursts of such high speed energy to enter said environment, the transmitter of high speed propagating energy on each object being controlled by an object mounted receiver adapted to respond to an appropriately encoded burst of such high speed energy, each said burst being encoded so as only to be responded to by one of the object mounted receivers (each transmitter/receiver combination being referred to as a transponder), to thereby initiate a burst of slowly propagating energy from the transponder, wherein the burst originating transponder location is identifiable from the encoding of the transmission which triggers that transponder and the burst is of just sufficient duration to provide a response at the receivers and in order to allow the system to adapt to different numbers of transponders and different demands for service, and a coordinating control system is provided for determining the order in which the object mounted transmitters are to be triggered by the encoded transmissions from the master transmitter, in response to updatable information relating to the service demands of the transmitter and/or transponders and/or objects.