Frederick G. Edwards, Peter V. W. Loomis

Peer Reviewed

Abstract: NASA Ames Research Center conducted a nonreal-time, Differential Global Positioning System (DGPS) flight-test experiment using two coarse-acquisition (C/A) code GPS receivers. The data were recorded concurrently at a fixed site and on board the NASA SH-3G test helicopter. The aircraft conducted several simulated mission operations, including terminal approach, while being tracked by radar and laser systems. After the flights, data recorded by the two GPS receivers and the trackers were analyzed to determine whether differential corrections could improve the navigation performance of the airborne GPS receiver. An airborne navigation error history was obtained by subtracting the reference “true” trajectory (derived from the tracking data) from the airborne GPS navigation solution. At the same time, differential GPS corrections were obtained by subtracting the ground-station GPS navigation solution from the true (surveyed) location of the ground receiver. Filtering was used to separate receiver-unique errors in the GPS data from the locally common (spatially correlated) GPS errors. The results show high correlation between airborne navigation errors and the differential corrections. The airborne navigation solution is shown to be much improved after the addition of the differential corrections. Efforts are continuing to develop a real-time differential data link between the ground station and the aircraft.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 32, Number 3
Pages: 233 - 253
Cite this article: Edwards, Frederick G., Loomis, Peter V. W., "CIVIL HELICOPTER FLIGHT OPERATIONS USING DIFFERENTIAL GPS", NAVIGATION, Journal of The Institute of Navigation, Vol. 32, No. 3, Fall 1985, pp. 233-253.
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