Technical Considerations for Long Range DGPS

Gordon T. Johnston and Peter J. Daly

Abstract:	The ability of Differential GPS (DGPS) to improve the accuracy of positioning over relatively small areas (cl00 kilometres) is well known. Over larger areas or long Reference Station to User distances (>500 Kilometres) the performance is neither adequately documented or understood although a considerable body of empirical data indicates good performance even at extended ranges. This paper describes in detail the practical and technical aspects that a long range DGPS system must address in order to ensure accurate and reliable positioning. For accurate offshore surveys, such as 3D seismic surveys, radio positioning systems, for example Syledis, are frequently specified and used. The introduction of, and the increasing coverage of, the GPS constellation has the potential to change this situation. Project based data examples using Racal’s SkyFix DGPS network are provided to illustrate the technical considerations. Influence on the performance from station siting, co-ordinate reference frames, DGPS datalinks, operating techniques and data recording systems are discussed. To achieve both accurate and reliable positioning in real time, the DGPS User must appreciate the influences on the positioning integrity.
Published in:	Proceedings of the 1993 National Technical Meeting of The Institute of Navigation January 20 - 22, 1993 Parc 55 Hotel San Francisco, CA
Pages:	261 - 271
Cite this article:	Johnston, Gordon T., Daly, Peter J., "Technical Considerations for Long Range DGPS," Proceedings of the 1993 National Technical Meeting of The Institute of Navigation, San Francisco, CA, January 1993, pp. 261-271.
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