Static and Dynamic Performance of a Novel GPS Attitude Determination Algorithm (GADA)

Nelson Paiva Oliveitre Leite and Fernando Walter

Abstract:	As previously presented at the ION GPS 2002 and IONNTM 2004 meetings, the satisfactory ability to determine an aircraft attitude, computed by a novel GPS attitude determination algorithm (GADA) has been demonstrated through simulations, ground tests and a flight-test campaign, where the GADA´s computed aircraft attitude angles were compared to a true attitude reference angles. The aircraft true attitude angles were provided by a complete Flight Tests Instrumentation (FTI) composed by a set of transducers, an airborne PCM Data Acquisition System (DAS) PCU-800 from L-3 Communication, a Teac AB-80-F 8mm airborne tape recorder and a GPS/IRIG-B time base, to allow the time correlation of all measurements. The flight test campaign was conducted at the Brazilian’s Flight Test Division T-25C 1956 Basic Trainer aircraft manufactured by EMBRAER. Measurements at the reference system are taken from a set of transducers, which are mounted on the aircraft’s instrumentation bay to provide attitude data at 32Hz rate. Carrier phase measurements at 10Hz rate are also acquired by the DAS for attitude post-processing. An accurate alignment procedure was employed to correct the misalignment from FTI, as well from the GPS antenna reference to the aircraft reference frames to remove all possible systematic errors. The algorithm uses doubledifferences approach and detects if a given Satellite is above or under the antenna array plane. The performance and accuracy of the system is demonstrated under static and dynamics tests, which are fully compliant with the Federal Aviation Administration (FAA) Advisory Circular (AC) 25-7A, that requires the maneuvering range of ±30 degrees for the pitch and roll angles for aircraft certification. An appropriate flight path was selected and carried out several times to allow the proper determination of the GADA characteristics as compared to REQUEST that is a well-known published algorithm. Data reduction analysis of all flights totaling 11:38 flight hours, demonstrated that GADA is more robust than REQUEST due to its characteristics. Also it is presented that GADA and REQUEST static accuracy is highly dependable of the Attitude Dilution of Precision (ADOP) while its dynamic accuracy depends upon the GPS receiver DPLL model and coefficients.
Published in:	Proceedings of the 2007 National Technical Meeting of The Institute of Navigation January 22 - 24, 2007 The Catamaran Resort Hotel San Diego, CA
Pages:	161 - 171
Cite this article:	Leite, Nelson Paiva Oliveitre, Walter, Fernando, "Static and Dynamic Performance of a Novel GPS Attitude Determination Algorithm (GADA)," Proceedings of the 2007 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2007, pp. 161-171.
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