Practical Investigations on DGPS For Aircraft Precision Approaches Augmented by Pseudolite Carrier Phase Tracking

Günter W. Hein, Bernd Eissfeller, Wolfgang Werner, Björn Ott, Bryant D. Elrod, Kevin Barltrop and James Stafford

Abstract:	In recent years, several approaches have been investi-gated to fulfill the high performance requirements of integrity, accuracy, availability and continuity of serv-ice for precision landings up to CAT-III. Additional sensors or augmentations are necessary to solve for the shortcomings of standalone DGPS. Some approaches propose to use the Russian GLONASS or GPS/INS integration, but so far none of them has been accepted as a solution. In this paper theoretical implications and practical experiment results of airport pseudolites (APL) for improving GPS performance with respect to high precision landing are discussed. Although the ideal view of an APL is a “satellite-on-the-ground“, there are many effects that have to be considered and modeled in a different way than for GPS signals. Among those are the “near-far“-problem, signal interference, time synchronization, tropospheric effects, orbit (APL location) errors and particularly, multipath. Whereas for satellite signals most of the error sources can be eliminated by single or double differencing the observation equations, fewer of the errors on the APL signals can be eliminated from the analogous APL equations, because of a totally different geometric situation. In case of the APL pseudoranges being contaminated with strong and even “standing“ multipath, the PL carrier phases can be used to get a high accuracy position fix. Different algorithms for using not only the APL code measurements but also the carrier phase of the signal have been implemented and tested. The effects of the APL carrier phase signal on ambiguity resolution have been investigated. Flight tests have been carried out by the Institute of Geodesy and Navigation (IfEN) at Braunschweig airport employing a Stanford Telecom Pseudolite in November 1996 and May 1997 to assess the capabilities and limitations of a combined DGPS/DAPL solution. Test results so far are presented on the characteristics of the APL signal received on-board the aircraft and real-time kinematic positioning.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1851 - 1860
Cite this article:	Hein, Günter W., Eissfeller, Bernd, Werner, Wolfgang, Ott, Björn, Elrod, Bryant D., Barltrop, Kevin, Stafford, James, "Practical Investigations on DGPS For Aircraft Precision Approaches Augmented by Pseudolite Carrier Phase Tracking," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 1851-1860.
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