The present invention is related to location positioning systems, and more particularly, to a method and apparatus for using satellite state information from two or more different satellite systems in navigation processing. According to one aspect, it makes use of GPS extended ephemeris functionality to produce satellite state vector estimates for GLONASS satellites. These satellite state vector estimates can be used alone or in combination with GPS satellite vectors to provide updates to the receiver's navigation processing. According to further aspects, the GLONASS satellite position and trajectory information is extrapolated with a GPS gravity model rather than the GLONASS model, thereby allowing it to be extrapolated more accurately and for longer periods of time than the GLONASS model allows.
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