Global positioning system using almanac data for a fast time to first fix

摘要

A system using coarse GPS orbital parameters for providing a precise GPS location. The system includes a GPS reference receiver and a GPS user receiver. Coarse locations-in-space of GPS satellites are computed from almanac or old ephemeris data. In a first embodiment the GPS user receiver uses DGPS corrections based upon the same coarse orbital parameters for providing a precise DGPS user location. In a second embodiment the GPS user receiver computes a coarse location from the coarse orbital parameters; and the GPS reference receiver recalculates the user pseudoranges using the same coarse orbital parameters and then uses the recalculated user pseudoranges for providing a more accurate user location.