Satellite LDGPS Network: System and Operational Parameters that can be used to Optimise End User Performance

Sue Hanna, Simon Birch,Vern Vogt

Abstract:	The first North American mobile satellite-based Local Differential Global Positioning System (LDGPS) commercial service was successfully launched for Geographic Data BC (GDBC), British Columbia Ministry of Environment, Lands and Parks, over the TMI MSAT-1 satellite in January, 1998. This service, known as the Global SurveyorÔ, was the culmination of 18 months of system development, testing, and implementation by the two partners operating the service, TMI Communications Inc. and Geographic Data BC. This paper lays out the design objective of the service, presents an overview of the real-time LDGPS network, looks at system performance issues that were discovered during the testing and demonstration phases (and the corresponding testing methodology used to investigate and resolve them), and discusses several conclusions that will facilitate the design and performance testing of similar satellite-based DGPS services. It is concluded that the key relationships in the design of a satellite LDGPS Network are: GPS Corrected Fix Performance to RTCM Received Messages, RTCM Received Messages Performance under varying message throughputs, and RTCM Received Messages to EIRP in a particular baseline test area. For the satellite LDGPS network, it appears that when using the Trimble ProXL receiver and an RTCM Age setting of 10 seconds, a 90% GPS Correction Fixes is a reasonable target performance under all operating conditions and this is roughly equivalent to a 60% RTCM Message Success Rate.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1455 - 1464
Cite this article:	Hanna, Sue, Birch, Simon, Vogt, Vern, "Satellite LDGPS Network: System and Operational Parameters that can be used to Optimise End User Performance," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1455-1464.
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