A Systems Approach to a National Position, Navigation and Timing Service

John W. Lavrakas

Abstract:	For years many have looked to GPS as “the” worldwide provider of global positioning, navigation, and timing ser- vices. Indeed, it is used for just this purpose in nearly every country of the world. Yet this “system” is in reality but one part of a national positioning, navigation, and timing service (PNT). In applications where GPS has been unable to pro- vide the necessary accuracy, reliability, and integrity, it has been augmented by other systems. These include ground- based and satellite-based services, including local area dif- ferential systems, the FAA’s Wide Area Augmentation Sys- tem, the maritime Differential GPS (DGPS) Service, as well as commercial GPS differential services, all of which have been developed more or less independently of one another. Conceptually, the overall utility of these individual services can be enhanced by formalizing the concept of a national positioning, navigation, and timing service. Such a service incorporates GPS as a core capability, but includes other space and ground-based technologies as well. This national service can provide separate levels of service to different user groups, such as: • Civil non-safety of life service – analogous to the cur- rent GPS Standard Positioning Service • Civil safety of life service – analogous to the current SPS with the addition of the planned third civil signal • Military services – analogous to the current GPS Pre- cise Positioning Service enhanced by the addition of new military signals This paper explores what is needed in order to evolve to- ward a national positioning, navigation, and timing service. It discusses the basic elements and services needed, the in- tended user community, and the benefits of such a service. This paper outlines a systems approach toward implement- ing such a service, including defining functional and per- formance requirements, creating specification documenta- tion, and establishing a formal systems engineering process. This paper was prepared under work being done by Over- look Systems Technologies, Inc. for the Office of the Assis- tant Secretary of Defense for Command, Control, Communi- cation, Intelligence.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	703 - 736
Cite this article:	Lavrakas, John W., "A Systems Approach to a National Position, Navigation and Timing Service," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 703-736.
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