Point positioning with the Navstar Global Positioning System

This study examines five weeks of Navstar Global Positioning System (GPS) data from the perspective of point positioning. Data are used from the GPS monitor sites and from the Defense Mapping Agency sites at Smithfield, Australia and Mahe, Seychelles. Navstar satellite ephemeris was determined by using the GPS monitor sites and also by using the DMA sites to augment the GPS tracking network. The latter station net provides some Southern Hemisphere coverage. Comparisons are provided between the postfit ephemerides determined by the respective tracking nets and between point positions at the tracking sites as determined by the respective ephemerides. An additional comparison is made between point positions of the DMA tracking sittes obtained from the postfit and broadcast ephemerides. All computations are carried out in the World Geodetic System of 1972.