Patent ID: 8654009

Claim:
A method comprising obtaining, by an end user GNSS receiver, a broadcast ephemeris data set associated with a GNSS; obtaining, by the end user GNSS receiver, a current position; measuring, by the end user GNSS receiver, a range to a first satellite to obtain a first pseudorange; determining, by the end user GNSS receiver, based on the current position and a synthetic ephemeris data set, an expected range to the first satellite to obtain a second pseudorange; determining, by the end user GNSS receiver, based on the first pseudorange and the second pseudorange, an error in the first pseudorange; attributing, by the end user GNSS receiver, the error only to clock error in the synthetic ephemeris data set; determining, by the GNSS receiver, whether the synthetic ephemeris data set is valid or invalid based, at least in part, on the broadcast ephemeris data set and a predefined criterion of acceptability, wherein determining whether the synthetic ephemeris data set is valid or invalid includes performing statistical analysis of clock differences between the broadcast ephemeris data set and the synthetic ephemeris data set according to the predefined criterion of acceptability; and in response to determining that the synthetic ephemeris data set is invalid, recalibrating, by the GNSS receiver, a clock correction parameter included in the synthetic ephemeris data set based on the clock error.