Wide Area Differential GPS Field Study

Ivan Catchpole, Peter R. Upton, Andrew Sinclair, Jim Nagle

Abstract:	Inmarsat commissioned the field study to be carried out by Signal Computing Ltd in association with the Royal Greenwich Observatory. The study aims to identify the commercial suitability of Wide Area Differential GPS (WADGPS) corrections. The corrections provided to users would be relayed via INMARSAT-3 geostationary satellites and are required to be valid over the footprint of an entire Inmarsat ocean region (approximately l/J of the Earth’s surface). The study has been conducted within the Inmarsat Atlantic Ocean Region East. Trials took place over a five month period to achieve a representative set of data. Six widely diitributed collection sites were used to ensure that the maximum duration of satellite data were received and that a representative model for atmospheric effects obtained. Analysis is restricted to the use of GPS carrier and phase data obtained using the C/A code transmitted by Block II satellites only. This paper presents the analysis of data collected during a four day trial period. The ability to determine the GPS satellite ephemeris (independent of GPS broadcast ephemeris), Klobuchar model parameters tailored to the oceanic region, and satellite clock corrections using GPS data obtained from this limited deployment of collection sites is addressed. The primary degradation effects on stand-alone GPS positioning of Selective Availability (SA) are corrected using WADGPS, resulting in a significant improvement in position accuracy.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	1223 - 1232
Cite this article:	Catchpole, Ivan, Upton, Peter R., Sinclair, Andrew, Nagle, Jim, "Wide Area Differential GPS Field Study," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 1223-1232.
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