Patent ID: 7164383

Claim:
A local area augmentation navigation system for determining the location of an object using differential GPS, the system comprising: at least two reference stations at known locations, each of the reference stations receiving a GPS signal from a GPS constellation and collecting and outputting the pseudo-range data from the GPS signal; a master station receiving the pseudo-range data from the reference stations, the master station forming a correction message from the pseudo-range data and the known locations of the reference stations, the master station broadcasting the correction message; a security receiver and an evaluation computer cooperating to monitor the broadcast of the correction message by the master station, to also monitor other broadcasts in the area for unauthorized broadcasts having a similar character as the correction message broadcast by the master station, and to output an alert signal upon detection of an unauthorized broadcast, the security receiver receiving the correction message broadcast by the master station via a first communication link, wherein the evaluation computer receives the correction message output by the master station via a second communication link different from the first communication link and determines that an unauthorized broadcaster exists when the message received by the security receiver does not match the correction message broadcast by the master station; and a LAAS receiver receiving the correction message broadcast by the master station as well as a GPS signal from the GPS constellation and calculating the location of the LAAS receiver with the correction message and the GPS signal.