Patent ID: 6104978
Filing Date: 2000-08-15
Classification: G01S

Abstract:
A method for identifying location of an asset to be tracked comprising the steps of:receiving signals transmitted from a plurality of Global Positioning System (GPS) satellites at said asset;detecting a GPS telmetry word preamble (TWP) and measuring data related to propagation differences between signals transmitted from GPS satellites and received at said asset;deriving satellite identifications for each of said GPS satellites;maintaining an auxiliary GPS (AGPS) data base and a GPS hand-over word (HOW) table to determine TWP start time at said asset;computing an estimated location of said asset from said measured data, AGPS and HOW data and a clock in approximate synchronization with GPS time;encoding and transmitting to a central station the satellite identifications and the computed estimated position;decoding, at said central station, data received from said asset; andcalculating, at said central station, a corrected location of said asset based upon the transmitted data and data derived from at least one receiver spaced apart from said asset.