Patent ID: 8035559

Claim:
A global positioning system (GPS) receiver comprising: a demodulator for obtaining ephemeris data and almanac data from a navigation message sent by a plurality of satellites; a calculator for calculating a plurality of almanac correction parameters according to coordinate differences between a plurality of ephemeris-based coordinates of said satellites and a plurality of almanac-based coordinates of said satellites and according to clock differences between a plurality of ephemeris-based clock drifts of said satellites and a plurality of almanac-based clock drifts of said satellites; and a satellite position calculator for calculating said ephemeris-based coordinates according to said ephemeris data, for calculating said almanac-based coordinates according to said almanac data, and for calculating a plurality of positions of said satellites according to said ephemeris data, said almanac data and said almanac correction parameters, wherein said calculator verifies validity of said ephemeris data, said almanac data and said almanac correction parameters and calculates a new plurality of almanac correction parameters if previous almanac correction parameters are invalid and said ephemeris data and said almanac data are valid.