Patent ID: 7400292
Filing Date: 2008-07-15
Classification: G01S

Abstract:
1. A method of operating a navigation system comprising the following steps: (a) transmitting GPS signals from a plurality of satellites; (b) monitoring the GPS signals transmitted by said satellites using a network of monitoring stations, said monitoring stations transmitting measurement information acquired during said monitoring step to a central station; (c) determining at said central station the integrity and reliability of the GPS signals transmitted by said satellites as a function of said measurement information received from said monitoring stations; (d) transmitting signals representing the integrity and reliability of the GPS signals transmitted by said satellites from said central station to said satellites, said integrity signals being in the form of user range accuracy messages, and said reliability signals being in the form of user range accuracy monitoring bits representing the health of each of said satellites; (e) transmitting updated GPS signals and not transmitting said reliability signals from said satellites, said updated GPS signals taking into account said integrity signals and said reliability signals, said transmitted updated GPS signals including integrity signals in the form of user range accuracy messages; (f) determining at a navigation receiver the range and position of each of said satellites based on said updated GPS signals received from said satellites by said navigation receiver; (g) determining at said navigation receiver the integrity of the determined position of each satellite as a function of the integrity signals included in said updated GPS signals; (h) determining at said navigation receiver the position of said navigation receiver based on the determined ranges and positions of said satellites; and (i) performing a task utilizing said determined position of said navigation receiver only if said reliability value is above a certain threshold.