Is DGPS still a good option for mariners?

Terry Moore, Chris Hill and Luis Monteiro

Abstract:	The International Maritime Organisation (IMO), in its Sub-Committee for the Safety of Navigation, has recommended the acceptance of GPS as a component of the World-Wide Radionavigation System. However, the IMO pointed out that GPS accuracy was not sufficient for harbour entrances and approaches and that GPS did not provide instantaneous integrity to alert users of any malfunction. The Sub-Committee considered that DGPS could improve significantly both the accuracy and the integrity of GPS. In fact, the transmission of differential corrections to the GPS signals allows elimination of most of the errors of GPS and improves significantly the integrity of the service: while GPS does not provide instantaneous integrity, the use of DGPS stations – which monitor permanently the signals of the visible satellites – enables the timely warning of any malfunction or failure in less than 15 seconds. However, the recent discontinuation of Selective Availability (SA), which led to an improvement in standalone GPS accuracy, has changed some of the premises that justified differential services. The needs of mariners in terms of radiopositioning / radionavigation are presented, with the aim of evaluating the ability of unaugmented GPS and of DGPS to comply with marine navigation requirements. The impact of the removal of SA on DGPS and its benefits for mariners is also discussed in order to show that DGPS is still adequate and useful for mariners.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	1598 - 1605
Cite this article:	Moore, Terry, Hill, Chris, Monteiro, Luis, "Is DGPS still a good option for mariners?," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 1598-1605.
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