Patent ID: 6020847
Filing Date: 2000-02-01
Classification: G01S,H04B

Abstract:
A method for determining a geolocation of a user terminal in a satellite based telecommunications system which passes communications signals along assigned channels between a user terminal, a satellite, and an associated earth station, said method comprising the steps of:receiving a telecommunications signal over an assigned channel from a user terminal at an earth station;determining a timing error offset representative of motion of said user terminal relative to said earth station and based on said telecommunications signal;combining said timing error offset with a round trip propagation delay representing round trip propagation time of an RF signal through said user terminal, a satellite, and said earth station to obtain an updated round trip propagation delay through said user terminal, said satellite, and said earth station;removing an earth station-to-satellite round trip delay from said updated round trip propagation delay, thereby determining a satellite-to-mobile terminal round trip propagation delay;determining a range solution line based on said satellite-to-mobile terminal round trip propagation delay;determining a Doppler solution line based on said telecommunications signal;determining geographic points of intersection of said range and Doppler solution lines; andoutputting one of said geographic points of intersection as a geolocation of the user terminal.