Patent ID: 7751974

Claim:
A method of verifying the validity of a Satellite Positioning Systems (SATPS) three-satellite solution for determining a receiver's location, comprising: obtaining a primary solution and an alternate solution using signals from the three SATPS satellites, wherein the primary solution and the alternate solution comprise least-square solutions that satisfy predefined pseudorange measurement constraints; separating the three SATPS satellites into a first pair of SATPS satellites and a second pair of SATPS satellites; measuring Doppler difference for the first pair of SATPS satellites, thereby obtaining a first measured value of Doppler difference; measuring Doppler difference for the second pair of SATPS satellites, thereby obtaining a second measured value of Doppler difference; computing a first estimated value of Doppler difference for the first pair of SATPS satellites, and a second estimated value of Doppler difference for the second pair of SATPS satellites; computing a first Doppler difference residual for the first pair of SATPS satellites by subtracting the first estimated value of Doppler difference from the first measured value of Doppler difference; computing a second Doppler difference residual for the second pair of SATPS satellites by subtracting the second estimated value of Doppler difference from the second measured value of Doppler difference; and comparing the computed first and second Doppler difference residuals to determine a valid solution from the primary and alternate solutions.