A data model is built by using satellite ephemeris data collected over an extended period of time, allowing generation on a server of very precise orbital parameters preferably using a force or numerical method. These orbital parameters are stored in a mobile device. When a First Fix is required by a GNSS system within the mobile device, these stored orbital parameters are used to rapidly generate accurate satellite trajectory data model without requiring access to a broadcasted ephemeris or a network connection. The stored orbital parameters may be modified in part or in whole as required bychanging coefficients of the stored parameters.