Real-Time Flight Test Evaluation of the GPS Marker Beacon Concept for Category III Kinematic GPS Precision Landing

Clark E. Cohen, Boris S. Pervan, David G. Lawrence, H. Stewart Cobb, J. David Powell, and Bradford W. Parkinson

Abstract:	A new system based on GPS Marker Beacons (low-power pseudolite transmitters situated underneath the approach path) has been developed to provide the highest possible accuracy, integrity, availability, and continuity for Category III Precision Landing with the Global Navigation Satellite System (GNSS). Two new developments are reported: l The highly-reliable real-time, centimeter-level kinematic GPS positioning using the GPS Marker Beacon concept is evaluated in flight testing. l A new paradigm for real-time differential GPS is introduced that eliminates the traditional data link. Two types of GPS Marker Beacons are considered: the Doppler Marker and the Omni Marker. The Doppler Marker is a low-power pseudolite with an independent time base, integrated with the ground reference receiver and a traditional data link. The Omni Marker rebroadcasts each received GPS signal coherently using a new PRN code. An aircraft receiving both the direct GPS signal and the new signal rebroadcast from the marker is capable of differential ranging without a digital data link. The latency associated with traditional differential GPS is completely eliminated. These components collectively comprise the Kinematic GNSS Landing System (KGLS). To evaluate the performance of the landing system, a series of approaches were flown in a Piper Dakota. Comparison with the NASA Ames laser tracker at Crows Landing demonstrates that the real-time position solutions obtained with GPS agree to within the 30 cm accuracy specification of the laser tracker. In independent testing at Palo Alto Airport, altitude accuracy above the runway is established to 10 cm using a laser altimeter.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	841 - 849
Cite this article:	Cohen, Clark E., Pervan, Boris S., Lawrence, David G., Cobb, H. Stewart, Powell, J. David, Parkinson, Bradford W., "Real-Time Flight Test Evaluation of the GPS Marker Beacon Concept for Category III Kinematic GPS Precision Landing," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 841-849.
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