WAAS Benefits of GEO Ranging

Timothy Schempp, Jason Burke, Arthur Rubin

Abstract:	WAAS enhances the GPS standard positioning service by providing sufficient integrity, accuracy, availability and continuity for use in commercial aviation. The system provides en-route through non-precision approach (LNAV), Lateral NAVigation / Vertical NAVigation (LNAV/VNAV), and Localizer Performance with Vertical guidance (LPV) approach capabilities. But WAAS is more than a navigation system for pilots. Most any GPS receiver you buy today is WAAS enabled allowing everyone from hikers and bikers to surveyors, farmers and rescue workers to enjoy the benefits of improved accuracy and integrity in their day to day activities. Over the last 3 years (2005-2008), WAAS has undergone significant expansion: adding reference stations in Alaska, Mexico and Canada, upgrading processing software, and replacing the legacy Geostationary Earth Orbit (GEO) satellites with new satellites that are positioned to give dual signal coverage in North America. GEO satellites serve as both the source of the WAAS correction message and as additional ranging sources which are always in view of the service region. This paper shows the positive benefits of using GEO satellites as precision approach quality ranging sources along with a discussion of the challenges faced when generating range corrections for single frequency geo stationary satellites. The analysis shows that the GEO provides a substantial improvement in WAAS availability in Alaska under nominal conditions and significant improvements everywhere in North America when GPS satellites are unavailable.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1903 - 1910
Cite this article:	Schempp, Timothy, Burke, Jason, Rubin, Arthur, "WAAS Benefits of GEO Ranging," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1903-1910.
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