Patent ID: 6127976
Filing Date: 2000-10-03
Classification: G01S,G06K

Abstract:
A method for identifying the geographical locations of objects having tags containing transmitters, a respective tag's transmitter being operative to transmit signals containing information identifying its associated tag, said method comprising the steps of:(a) receiving, at a plurality of geographically dispersed receivers having known geographical positions, signals transmitted from one or more of said tags;(b) processing signals received in step (b) at each of a plurality of detection processors to which receivers receiving signals from a tag in step (a) are coupled, so as to determine the earliest time-of-arrival of signals received thereby from said tag;(c) assembling, at said each of said detection processors, a respective message containing the identification of said tag and the earliest time-of-arrival of signals received therefrom by a receiver to which said each detection processor is coupled;(d) transmitting messages assembled in step (c) by said detection processors for multiple tags to a plurality of association processors, and such that messages assembled in step (c) by said detection processors for the same tag are transmitted to the same association processor, each association processor being operative to store contents of messages received from one or more detection processors as a respective association report for a respective tag; and(e) transmitting association reports stored by said association processors in step (d) to a plurality of location processors, each of which is operative to determine the geographical location of tags identified in association reports received thereby, in accordance with time-of-arrival information for said tags contained in said association reports.