Analysis of Maritime DGPS Positioning Accuracy at Sea

L.S. Monteiro, P.R. Marreiros

Abstract:	Portugal has recently inaugurated a Differential GPS (DGPS) network to support maritime users. Two DGPS broadcast stations were installed at Cape Carvoeiro and Sagres. The transmission of differential corrections to the GPS signals is expected to allow elimination of most of the errors of GPS providing accuracies generally better than 3 m. The extra accuracy of DGPS is particularly important in pilotage waters, namely inside harbours, where the navigation requirements are the most demanding, due to the close proximity to dangers. In order to evaluate positioning accuracy parameters, a sea trial was conducted in harbour and coastal areas, onboard a survey vessel of the Portuguese Hydrographic Office. One geodetic grade GPS antenna was installed onboard and the signal fed two GPS receivers trough an antenna splitter. One was a L1 code GPS receiver connected to a DGPS beacon antenna. The other was a geodetic grade receiver that collected code and phase raw data for post processing in GPS kinematic mode. This paper describes the accuracy results obtained using the signal broadcast by the Portuguese DGPS stations. The reference positions, with which DGPS was compared, were the geodetic GPS post-processed solutions, which have accuracies in the decimetre level and are, therefore, accurate enough to evaluate DGPS expected accuracy.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	38 - 44
Cite this article:	Monteiro, L.S., Marreiros, P.R., "Analysis of Maritime DGPS Positioning Accuracy at Sea," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 38-44.
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