Concepts to Limit Convergence Time of GPS-Based Precise Point Positioning (PPP)

PPP has become a popular technique to process data of isolated GPS stations. Unfortunately zero-difference ambiguity resolution and subsequently extended convergence time are still not sufficiently resolved issues of this technique. This paper deals with first results of the 'Regional satellite Clocks' PPP approach. Precise satellite clock information is adapted to cover regional delay effects. This technique makes use of one nearby reference station (master station) which is affected by spatially and temporally correlated error sources. When introducing the Regional Clocks via a PPP solution to process the coordinates of an isolated station we get rid of the remaining master station clock which will be absorbed by the slave station clock. The satellite specific bias at the master station will be absorbed as well by the ambiguity parameter at the slave station. In terms of convergence time which will be reduced in any case down to 30 minutes or less, this procedure is clearly favourable. The accuracy is quite comparable with state of the art PPP procedures. Nevertheless, this approach cannot compete in fixing times with DD approaches but the correlation holds over hundreds of kilometres distance to the master station and the clock differences can easily by obtained, even in real-time. The regional clocks approach is one out of four methods investigated within the research project RA-PPP (funded by the Austrian Research Promotion Agency). A PPP software module that applies the developed algorithms and techniques to real GPS data is set up during the research project. PPP is performed by means of a commercial GPS receiver supported by a small processing device. Several testing and verification routines evaluate the performance of applied algorithms and individual calculation steps. Also a later modification with regard to GNSS modernization (new signals) is considered.