Performance Analysis of an Integrated GPS/LORAN-C Tracking System

J. Carroll

Abstract:	The rapidly increasing use of satellite navigation encompasses a broad range of civilian users. Not all users are sufficiently aware of important operational risks in using, say, the Global Positioning System (GPS) for positioning, navigation and timing (PNT) applications. Systems that use GPS work very well when designed properly, and when sufficient robust ranging signals from the satellites are available. When the GPS signal cannot be used for PNT, appropriate backup systems and procedures should be used. Service providers are increasingly aware of the need to provide adequate system integrity, and to provide a seamless procedure for timely switches to and from the backup procedures. As a result, there is increasing interest in integrated PNT systems. Over the past several years the Volpe Center has installed vessel surveillance and tracking systems for maritimeapplications in several waterways worldwide. This includes systems to enhance maritime security by providing increased situational awareness. Currently, the Volpe Center is completing the installation in the Mediterranean of a new generation of transponder equipment for use by harbor protection forces in both domestic and foreign ports. This evolving technology is now being applied to surface applications in urban areas in the U.S., using positioning and timing information provided by an integrated GPS/Loran-C/dead reckoning system. An important issue for the integrated GPS/Loran system is how well Loran and dead reckoning (DR) systems can supplement GPS when the GPS signal is not usable. Performance requirements vary with application, but a basic requirement in urban areas is reliable location of the vehicle at an intersection. This paper describes the design and uses of an integrated GPS/Loran/DR tracking system, and presents results from performance evaluations conducted in New York City, including the Lower Manhattan financial district. The results obtained show that eLoran can be an effective backup to GPS in many areas of Manhattan, including some dominated by tall buildings or open tunnels, where GPS is not able to function well. Both GPS and Loran - whether separate or integrated – cannot, however, sustain performance in 'deep urban canyon' areas such as New York's financial district. A well-designed DR system, perhaps aided by an optical system, will likely be a necessary supplement in these areas. Although an asset, not all DR systems will operate effectively unless their design is totally independent of GPS conditioning. Disclaimer. The statements and opinions in this paper are the authors only, and they do not necessarily reflect policy or opinions of the U.S. Government.
Published in:	Proceedings of the 2006 National Technical Meeting of The Institute of Navigation January 18 - 20, 2006 Hyatt Regency Hotel Monterey, CA
Pages:	615 - 628
Cite this article:	Carroll, J., "Performance Analysis of an Integrated GPS/LORAN-C Tracking System," Proceedings of the 2006 National Technical Meeting of The Institute of Navigation, Monterey, CA, January 2006, pp. 615-628.
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