IMPROVEMENT OF PRECISE AND RELIABLE KINEMATIC GPS POSITIONING IN REAL-TIME OVER LONG DISTANCES
(Centre de recherche en géomatique, Université Laval, Ste-Foy, Québec,G1K 7P4, Canada
Claude St-Pierre (VIASAT Géo-Technologie, Montréal, Québec, H2S 1Z2, Canada
This research project, which is part of the Canadian GEOID (Geomatics for Informed Decisions) Network of Centres of Excellence, is dedicated to the improvement of the methodology and the algorithms to achieve more precise and more reliable kinematic GPS positioning (which implies more reliable and efficient phase ambiguity resolution) over distances even longer than 75 km: for the support, but not exclusively, of bathymetric surveys in real-time. This research will lead to added-value for the customized software already developed for the Canadian Coast Guard (CCG) and this will consequently further support the modernization and the cost-effectiveness of bathymetric operations. To reach these goals, different research avenues will be considered. The main avenues are: i) GPS relative positioning with multiple reference stations, ii) the improvement of ionospheric modeling, iii) the use of precise real-time orbits, iv) the integration of Glonass observations and v) radio-communication management (which includes the problem of time latency).
In this presentation, first results related to the interpolation of relative ionospheric delays will be presented. Ionospheric information is extracted from the reference stations - about 125 km apart in our case, along the St. Lawrence river. It is shown that this significantly improves the success rate of ambiguity resolution of phase observations collected by a GPS receiver onboard a survey ship navigating midway between two reference stations.