| 摘要 |
A GNSS enabled mobile device receives GNSS signals from visible GNSS satellites. Broadcast ephemeris is extracted from the received GNSS signals for generating ephemeris extension (future ephemeris) in the next several days for each of the visible GNSS satellites. The GNSS enabled mobile device uses the generated future ephemeris to determine a position fix even without fresh broadcast ephemeris completely received from the visible GNSS satellites. The generation of future ephemeris is scheduled according to the age of available ephemeris extensions and/or the time of visibility. Available ephemeris such as extracted broadcast ephemeris are integrated into an orbit model using the multi-step numerical integration methods and propagated to generate future ephemeris. The generated future ephemeris is reformatted into a desired orbit model and/or format of the GNSS enabled mobile device. A curve fitting polynomial of generated future ephemeris is stored instead of actual generated future ephemeris to conserve storage space. |
