Patent ID: 6618004
Filing Date: 2003-09-09
Classification: G01S

Abstract:
A differential positioning system for at least one mobile GPS user comprising:a central processing facility, a plurality of reference stations with known geographic locations or positions, means for each reference station to receive GPS signal data, means for each reference station to communicate with the central processing facility, wherein measurement data are sent to the central processing facility where differences between the received measurement data and the known locations of the reference stations are calculated, an error model that is generated from the calculated differences, the error model covering at least the area including the central processor and all the reference stations, means for two way communicating between the at least one mobile user and the central processing facility, means for the mobile user to receive GPS signal data, wherein the mobile user sends measurement data to the central processing facility, and receives corrected positional data for the mobile user therefrom, wherein the central processor uses the error model to calculate the corrected positional data for the mobile user, and means for the mobile user to generate a local error or offset from the last corrected position received as compared to its received GPS signals and then to use this offset when the mobile user is calculating its own position from the locally received GPS signals.