B. David McNally, David N. Warner, Jr., Daniel M. Hegarty, Thomas A. Schultz, and Richard Bronson

Peer Reviewed

Abstract: A flight-test evaluation of precision-code differential GPS for terminal approach and landing was conducted at the NASA Ames Research Center. Differential corrections to satellite range and range-rate measurements were computed in a stationary ground reference system, uplinked to the test aircraft, and used to correct corresponding airborne satellite data. Differentially corrected range and range-rate data, combined with inertial data, were then used with satellite position and velocity to compute aircraft position and velocity using an eight state extended Kalman filter. The airborne differential GPS (DGPS) solution was used to drive standard approach guidance instruments in the cockpit. Final approaches were flown from 4-7 mi out at 120 kn. The aircraft was laser tracked during each approach to determine its “true” position. Real-time DGPS positioning accuracy at the 200 ft decision height on a standard 3 deg approach was -0.1 m (mean) 20.9 m (l-sigma) cross-track, and -0.7 m (mean) 2 2.6 m (l-sigma) vertical. Real-time DGPS positioning accuracy based on analysis of the complete approach was 0.1 m (mean) 2 0.9 m (l-sigma) cross-track, and -0.8 m (mean) +- 3.3 m (l-sigma) vertical. The DGPS navigation system was compatible with standard flight director guidance systems. Pilots commented that the DGPS-based guidance appeared smooth and visually accurate.
Published in: NAVIGATION: Journal of the Institute of Navigation, Volume 39, Number 2
Pages: 155 - 176
Cite this article: McNally, B. David, Warner, David N., Jr.,, Hegarty, Daniel M., Schultz, Thomas A., Bronson, Richard, "FLIGHT TEST EVALUATION OF PRECISION-CODE DIFFERENTIAL GPS FOR TERMINAL APPROACH AND LANDING", NAVIGATION: Journal of The Institute of Navigation, Vol. 39, No. 2, Summer 1992, pp. 155-176.
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