PPP: Precise Point Positioning – Constraints and Opportunities

Abstract

Precise Point Positioning (PPP) is a satellite based positioning technique aiming at highest accuracy in close to real-time. First investigations using dual frequency data from a single GPS receiver data for a few cm-positioning in post-processing mode have been published in 1997 by JPL. Utilizing the ionosphere free linear combination the remaining required model information like precise orbits and clocks issued by the IGS has been used. Within the last decade a number of approaches have been carried out to serve applications in close to real-time by this technique. In comparison with common techniques like DGPS or RTK, the costs are reduced, because no base stations and no simultaneous observations are necessary. On the other hand the necessary models have to be fetched either from globally acting services like IGS (orbits, satellite clocks) or from regional GNSS service providers (atmospheric delays) and standard interfaces (e.g. RTCM) have to be developed to forward this information to the rover. Further problems still to be solved are coordinate convergence periods of up to 2 hours as well as ambiguity resolution, which are harmed by non-integer calibration phase biases. These biases vanish only in difference mode and have to be determined a priori. The main focus of the research presented in this paper is to enhance the actual achievable