Long Baseline Differential GPS Results via Starfix Data Link

L. E. Ott

Abstract:	Starfix is an independent navigation system utilizing signals relayed through geosynchronous satellites. The system was primarily developed to serve the offshore oil industry in the North American continent. The system was made operational in 1986 and in order to prove its accuracy and stability a second navigation system was needed to provide comparison data. Many tests were conducted using shore based radio navigation systems which proved the overall accuracy of the Starfix system. However, due to the high operational costs of oil exploration it became apparent that an additional means to check the Starfix system was necessary. This requirement was the driving impetus of the addition of Differential GPS transmissions over the Starfix data link. Differential GPS was an extremely cost effective means to provide the quality control to the Starfix system. Since the fall of 1986, DGPS service has continually been provided to Starfix users from two positions in the U.S. These sites are located at Houston, Texas and Miami, Florida. The baseline length between these two sites is 1700 kilometers. This means that a vessel operating in the Gulf of Mexico is no further than 850 kilometers from a differential GPS base station. Additional differential sites have been used at various times at locations at Mercedes, Texas; Long Island, New York; San Diego, California: Everette, Washington; and Lafayette, Louisiana over the last three years. This paper will present results from various baseline configurations of data collected over the last three years. Data are presented showing accuracy and stability results of a sequential GPS receiver and continuous tracking receiver. This paper describes the implementation of the Starfix Differential GPS network and demonstrates the achievable accuracies of DGPS with and without selective availability implemented on the GPS satellites. Future implementation of the Starfix Differential GPS service is also discussed concerning transmission rates and real time ephemeris tracking.
Published in:	Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989) September 27 - 29, 1989 The Broadmoor Hotel Colorado Spring, CO
Pages:	313 - 318
Cite this article:	Ott, L. E., "Long Baseline Differential GPS Results via Starfix Data Link," Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989), Colorado Spring, CO, September 1989, pp. 313-318.
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