GNSS orbit prediction with enhanced force model

Orbit prediction algorithms can be used in a portable positioning device to reduce the Time to First Fix and to augment the received broadcast ephemeris. In this work, we study the two-week prediction accuracy improvement that can be obtained when adding some smaller forces to our previously developed algorithm. These forces arise from solid earth tides, relativity effect, and the gravitational pull of Venus and Jupiter. Also, a box-wing model of solar radiation pressure is considered. The new model with aforementioned extra forces is tested for GPS, GLONASS and Beidou satellites using initial conditions computed from precise ephemerides. It is found that the enhancements give small but not negligible improvement, with more accurate Sun and Moon coordinates having the most effect and relativity correction for Earth's gravity the least. However, the improvements come at the cost of noticeable increase in computational load.