Satellite Navigation Accuracy and Availability Modeling as an Air Traffic Management Tool

Mitch Sams, A.J. Van Dierendonck and Quyen Hua

Abstract:	The impending development of next generation satellite- based navigation systems, such as the Wide Area Augmentation System (WAAS) and the Local Area Augmentation System (LAAS), has highlighted the need for an accurate systems design tool, and the eventual need for a new ATC management tool for these unique systems. Much different than traditional navigation systems, satellite-based systems will require accurate knowledge of satellite failure rates, constellation geometry and orbital accuracies in combination with the associated air and ground equipment performance accuracies and reliability. This information is then used to determine the availability of the navigation system as a function of time and geographic location. This vital information must be available to air traffic control personnel and users in near-real time. This paper describes the Wilcox Availability Coverage Model (WACM) - a tool initially developed as a systems design model, which can in the future be used as an on- line system availability tool to facilitate ATC management. The space component, airborne user and ground components are characterized to include performance parameters such as geometric precision, multipath and clock errors as well as ionospheric and tropospheric errors. Individual GPS and geostationary (GS) satellite errors are characterized as a function of elevation angle and then summed in every possible multiple satellite failure combination. Several issues will be addressed in the coming year in regards to performance availability of wide and local area GPS system performance and the associated architecture designs needed to meet these requirements. The development of a higher fidelity model, such as described here, will lead to more accurate performance predictions.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	203 - 213
Cite this article:	Sams, Mitch, Van Dierendonck, A.J., Hua, Quyen, "Satellite Navigation Accuracy and Availability Modeling as an Air Traffic Management Tool," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 203-213.
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