The FAA's WIB/WDGPS Testbed and Recent Test Results

Marie E. Lage and Bryant D. Elrod

Abstract:	The FAA is investigating the use of an independent ground monitoring network and geostationary satellites to enhance GPS performance in terms of integrity, accuracy and availability. Ground and airborne elements of a testbed are being developed for evaluation of the GPS Wide-Area Integrity Broadcast/Wide-Area Differential GPS (WBVWDGPS) approach to meet integrity warning and accuracy requirements in all flight phases through Cat I or “near” Cat I precision approaches. The current testbed consists of a user platform (UP) on board an FAA aircraft, a reference monitor station (RfMS) and central processing facility (CPF) located at the FAA Technical Center in Atlantic City, NJ. up to three remote monitor stations (RMSs), and an earth station (ES) located at Southbury, CT. GPS measurement data is collected by the RMSs and R&IS and provided to the CPF for use in developing integrity information and WDGPS corrections. The integrity information and WDGPS correction data are transmitted to the ES and broadcast to the UP via an Inmarsat 2 geostationary satellite. The message format is a subset of the WIB/WDGPS message format currently proposed by RTCA SC-159. Phase I activities have focused on testbed hardware integration and software development, preliminary WDGPS testing with a limited monitoring network (r 4 stations) and GPS integrity algorithm assessment. Initial flight tests were conducted during March 1993 at FAATC. The aircraft positioning performance (sensor accuracy) for WDGPS and LDGPS was analyzed along a 3 nmi approach path at FAATC. The WDGPS results (based on a single remote monitor station, 500 miles away) were within 6.1 meters in the vertical directions at the 95% probability level on the basis of 380 data points acquired. More extensive testing is underway to validate both WIB and WDGPS performance with an expanded monitor station network (I 3 stations). This paper presents an overview of the FAA WIBAVDGPS testbed, some results from recent flight test results and plans for further testing.
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:	487 - 493
Cite this article:	Lage, Marie E., Elrod, Bryant D., "The FAA's WIB/WDGPS Testbed and Recent Test Results," 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. 487-493.
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