DGPS Accuracy Observations and Potential Data Channel Improvements

R. Hartnett, K. Gross, B. Bovee, S. Nassar, G. Johnson, G. Sanders, P. Swaszek, D. Wolfe

Abstract:	The Coast Guard currently operates a maritime differential GPS service consisting of two control centers and over 60 remote broadcast sites. This service broadcasts GPS correction information on marine radiobeacon frequencies to improve the accuracy and integrity of GPS. The stated accuracy is 10 meters in all coverage areas (with typical accuracy much better than this), however to date there has been no comprehensive study of the current absolute accuracy achieved in a post-SA environment. The Coast Guard Academy was tasked by the Coast Guard Command and Control Center (C2CEN) with measuring the absolute accuracy observed with the Coast Guard DGPS system. A test system using several commercially available DGPS receivers as well as a standard GPS and a WAAS receiver for comparisons was developed. This test system was used at various distances and bearings from a Coast Guard transmitter site in order to assess the spatial variance in the accuracy of the positions. At each test location, positions were recorded at 1 second intervals for a period of 6-12 hours, and the 2 DRMS error was calculated. Preliminary results of this testing conducted in Spring 2003 are presented, together with comparisons to GPS and WAAS-corrected GPS accuracies. Finally, we introduce an idea for "overlaying" a second (higher data rate) MSK correction channel with minimal impact on the DGPS legacy channel, in support of those whose applications demand improved accuracies. This work was conducted as a research project by the Coast Guard Academy supported by the Coast Guard C2CEN.
Published in:	Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003) June 23 - 25, 2003 Hyatt Regency Hotel Albuquerque, NM
Pages:	518 - 527
Cite this article:	Hartnett, R., Gross, K., Bovee, B., Nassar, S., Johnson, G., Sanders, G., Swaszek, P., Wolfe, D., "DGPS Accuracy Observations and Potential Data Channel Improvements," Proceedings of the 59th Annual Meeting of The Institute of Navigation and CIGTF 22nd Guidance Test Symposium (2003), Albuquerque, NM, June 2003, pp. 518-527.
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