GPS SINGLE POINT POSITIONING WITH SA OFF: HOW ACCURATE CAN WE GET?

Abstract The announcement by U.S. President Bill Clinton to turn off ‘Selective Availability’ at midnight (Washington DC time) 1 May 2000 caught everyone by surprise. This decision to stop degrading the accuracy of the Global Positioning system's (GPS) Standard Positioning Service (SPS) will have a significant impact on users all over the world. One important outcome for the geomatics community is that the substantial improvement to GPS Single Point Positioning (SPP) results could make it an attractive alternative to the Differential GPS (DGPS) mode of positioning. In this paper some results from different SPP processing strategies are presented, and the accuracy improvement in the case of averaged static solutions is discussed. Finally, the paper speculates on the attainable SPP accuracy using single-frequency GPS receivers when the ionospheric activity is less intense in the future.