Optimising availability and continuity of the Portuguese DGPS network

Terry Moore, Chris Hill, and Luís Sardinha Monteiro

Abstract:	At ION GPS 2001, held in Salt Lake City, the authors presented a paper entitled “Is DGPS still a good option for mariners?”, which addressed the current need for a DGPS service, given the discontinuation of Selective Availability [Ref. 1]. In that paper, the benefits of DGPS for mariners, namely in terms of accuracy and integrity, were discussed and presented, in order to show that the option to embrace DGPS was, and is, still valid, because it can provide ships the best accuracy and integrity at sea. However, the accuracy advantage afforded and the integrity check performed by DGPS are only useful if the DGPS service reaches very high standards of availability and continuity. It would be almost useless to have a DGPS service with low availability and continuity, because it could mean a ship losing the differential corrections in restricted waters, where the service is more needed. In summary, the level of benefit gained from DGPS is directly proportional to the user availability of the service and to its continuity. Therefore, after having discussed accuracy and integrity last year, the authors will discuss, in this paper, issues related with availability and continuity (continuity replaced the previously used concept of reliability). The availability and continuity requirements recently adopted by the International Maritime Organization (IMO) and the International Association of Lighthouse Authorities (IALA) will be presented, as well as the ways by which DGPS services can meet the very high requirements for the harbour entrance and approach phase of navigation, particularly in the Portuguese DGPS network. The concepts used in the Portuguese DGPS network to minimize downtime and ensure the highest reliability and availability, will also be presented.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2696 - 2702
Cite this article:	Moore, Terry, Hill, Chris, Monteiro, Luís Sardinha, "Optimising availability and continuity of the Portuguese DGPS network," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 2696-2702.
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