GPS positioning with broadcast and precise ephemerides

The precise ephemeris and space vehicle clock corrections computed routinely by the International GPS Service for Geodynamics (IGS) under the International Association of Geodesy (IAG) is accurate to less than submeter. Since the precise orbit/clock is free from selective availability (SA) errors, accurate point positioning and orbit determination can be achieved if it is done with high quality pseudorange data in a post-mission mode. In this paper we present results of two applications of the precise orbit/clock: 1) the single point positioning of a fixed site, and 2) the onboard orbit determination of the OREX (Orbiting Re-entry Experiment) spacecraft.