Patent ID: 7830304

Claim:
A method of locating the position of a satellite in a satellite positioning system, the method comprising: receiving, at a terminal, satellite positioning data for at least one specified time period over a communications channel; storing, at the terminal, the satellite positioning data for the at least one specified time period; responsive to an event at a later time, calculating, at the terminal, the satellite position at the later time based on the satellite positioning data for the at least one specified time period, wherein the satellite positioning data for the at least one specified time period comprises ephemeris data for a first time period received at a first time, ephemeris data for a second time period received at a second time, and ephemeris data for a third time period received at a third time; estimating positions of the satellite at the first and second times using the ephemeris data for the third time period; calculating errors in the estimated positions at the first time using the ephemeris data for the first time period and at the second time using the ephemeris data for the second time period wherein the calculation of errors comprises fitting a curve to the errors and using the curve to give an extrapolated error value at the later time and calculating the position of the satellite at the later time from the ephemeris data for the third time period and the extrapolated error value.