Wide Area Augmentation System Vertical Accuracy Assessment in Support of LPV200 Requirements

Bill Wanner, Bruce Decleene, David A. Nelthropp, and Stephen Gordon

Abstract:	The FAA plans to provide LPV200 service to WAAS users, which will reduce the LPV approach decision height to 200 feet. This requires the WAAS meet a more stringent vertical accuracy of 4 meters 95% of the time with a vertical alert limit (VAL) of 35 meters. The William J. Hughes FAA Technical Center was tasked to demonstrate that the present WAAS meets the LPV200 accuracy requirement over the CONUS service area. This paper presents the data analysis conducted to validate WAAS vertical accuracy and the results of the vertical error analysis of the WAAS system. Validation of WAAS vertical accuracy was required under varying satellite conditions as well as degraded system operation, including ionospheric storms, GPS satellite failures, and WAAS signal in space interruptions. In order to verify accuracy over a wide area WAAS vertical error data was utilized from 20 reference receivers located in CONUS between July 2003 and June 2006 was used in the analysis. Vertical position error (VPE) data was collected at a 1Hz rate from each receiver over the evaluation period of three years. A total of 1,761,676,343 samples, which is equal to 20,390 receiver days, were loaded into the WAAS performance database for analysis. Another element of the analysis required that any VPE outliers greater than 8 meters be investigated to determine the cause and the characteristics of the errors. The data from 20,390 receiver days also provided a unique opportunity to characterize WAAS vertical performance and correlate VPE with vertical protection level (VPL) and vertical dilution of precision (VDOP).
Published in:	Proceedings of the 63rd Annual Meeting of The Institute of Navigation (2007) April 23 - 25, 2007 Royal Sonesta Hotel Cambridge, MA
Pages:	468 - 478
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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