An Analysis of Differential and Absolute GPS Aircraft Positioning

Gérard Lachapelle, M. Elizabeth Cannon, Weigen Qiu, and Chris Varner

Abstract:	The accuracy performance of single point (absolute) aircraft positioning using post-mission precise orbit and 30-s satellite clock corrections provided by permanent GPS tracking network services under Selective Availability is analyzed. The method and the permanent GPS tracking stations used to derive the post-mission ephemerides are described. The single point and DGPS positioning approach used to obtain the coordinates of the aircraft is summarized. Aircraft single point position accuracy is assessed through a comparison of the single point coordinates with corresponding DGPS-derived coordinates. The platform utilized for the evaluation is a Naval Air Warfare Center P-3 Orion aircraft. Single frequency all- in-view Narrow Correlatorm spacing C/A code Ll receivers are used for the flight tests. Data collected over a period of about 40 hours, spread over six days, off Florida’s East Coast in July 94, with DGPS reference stations in Jacksonville, FL, and Warminster, PA, form the basis for the study. The use of a second reference station was made to assess the effect of station location and distance from the aircraft on the consistency of the DGPS solutions. The analysis of results shows that the consistency between aircraft single point and DGPS coordinates obtained in single point positioning mode and DGPS mode is about 1 m (rms) in latitude and longitude, and 2 m (rms) in height, with instantaneous errors of up to a few meters due to the effect of the ionosphere on the single point Ll solutions.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	701 - 710
Cite this article:	Lachapelle, Gérard, Cannon, M. Elizabeth, Qiu, Weigen, Varner, Chris, "An Analysis of Differential and Absolute GPS Aircraft Positioning," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 701-710.
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