Wide area differential corrections (WADC) from global beam satellites

The author describes an Inmarsat sponsored R&D study investigating the requirements for wide area differential corrections, while minimizing the total transmission data rate and the number of reference stations. Wide area is taken to mean one Inmarsat ocean region (i.e. that part of the Earth´s surface illuminated by one geostationary satellite´s global coverage beam, approximately ±70 degrees in latitude and longitude) or significant portions thereof. It is Inmarsat´s initial premise that, to achieve this objective, the wide area differential correction system will need to be able to separate the sources of error on the GPS (Global Positioning System)/GLONASS signals received into three fundamental groupings: satellite position (as calculated from the broadcast ephemerides), propagation path deviations (ionospheric and tropospheric delay variations), and satellite clock displacements/deviations. The R&D study will be conducted in two phases: an analysis phase and an experimental phase. The analysis phase of the R&D effort is discussed