Experimental GBAS Performance at the Approach Phase

S. Saitohi, S. Fukushima, T. Yoshihara, N. Fujii

Abstract:	Electronic Navigation Research Institute (ENRI) in Japan has been developing and evaluating Ground Based Augmentation System (GBAS). We installed an experimental GBAS ground station and executed the approach .ight experiments at Sendai airport for testing the performance of the experimental GBAS. Our GBAS experimental ground subsystem consists of a VHF Data Broadcast (VDB) system, a data processing workstation (WS) for generating GBAS augmentation messages and four reference stations with GPS receivers, GPS antennas, personal computers (PC) and modems. The GPS antennas of the reference stations were installed along A-runway of Sendai airport in front of Iwanuma branch of ENRI. The phase center heights of these antennas were 1.5 meters. The tests were carried out with the experimental aircraft loading a GBAS VDB receiver, GPS receivers and a PC for a GBAS airborne station for computing its di.erential GPS (DGPS) positions and recording GBAS data. We executed approach and touch-and-go .ights from 1,500 feet altitude in order to check the accuracy, availability and compatibility with di.erent GPS receivers of our experimental GBAS at the .nal approach region. In these experiments, we also executed post-processed kinematic carrier-phase di.erential positioning to get reference positions. Using the same type of GPS receivers of ground and airborne subsystem in 2002 experiments, the vertical NSE (95%) were about 0.49 meters to 0.85 meters at the region from 0 to 1 nautical miles (NM) from runway threshold. Comparing the vertical NSE with CAT-II and CAT-III speci.cations of RTCA/DO- 245 (2.0 m), the results were satis.ed with these values. The results of comparison of 5.3 meters (CATII/ III Vertical Alert Limit speci.cation) and Vertical Protection Level values showed that the availability at the final approach region was about 96%. The system didn’t have enough availability for CAT-II and CATIII, whose requirement was 99% ~ 99.999%. We checked the over-bounding problem of GPS receiver compatibility of di.erent manufacturers. Therefore, we conducted the .ight experiment with two types of airborne GPS receivers. One was using the same type of receivers for airborne and ground and the other was using the di.erent type of receiver for airborne from the ground reference receivers. The results showed that GBAS positioning errors using the di.erent type of receivers increased slightly, but the accuracy met CAT-II and CAT-III speci.cations of RTCA/DO-245 and the availability was the same as using the same type of the ground receivers.
Published in:	Proceedings of the 2003 National Technical Meeting of The Institute of Navigation January 22 - 24, 2003 Disneyland Paradise Pier Hotel Anaheim, CA
Pages:	317 - 325
Cite this article:	Saitohi, S., Fukushima, S., Yoshihara, T., Fujii, N., "Experimental GBAS Performance at the Approach Phase," Proceedings of the 2003 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2003, pp. 317-325.
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