PERFORMANCE EVALUATION OF SEVERAL WIDE-AREA GPS SERVICES

Several wide-area services are currently available to GPS users. Some of these systems are commercial (e.g. OmniSTAR), and others are provided by government agencies (e.g. WAAS, Global Surveyor). The intent of this paper is to compare these three wide-area services in terms of achievable accuracy and also age of corrections. An experiment was conducted whereby these systems were evaluated side-by-side using similar GPS receiver technology and antenna splitting such that system errors could be isolated from receiver-dependent errors and multipath. Data over a 24 hour period is analyzed in realtime and post-mission and several solutions are compared. The real-time results were in the range of 1 m horizontal and 1.5 m vertical for the OmniSTAR and WAAS systems, and about 2-3 times poorer for the Global Surveyor service which are in part due to some latency problems. In general, the real-time results agreed well with the post-mission performance. Each of the systems tested is described and the results of each system, in both real-time and post-mission are described and discussed.