Development and Evaluation of a Precision Coordinate Transfer System for SRGPS

In Soo Ahn, Ray Breslau and Jim Sennott

Abstract:	The transfer of sensor data from multiple observation points to a common reference location arises in a number of aerospace and marine applications. Among factors that degrade measurements during transfer are structural flexures and uncertainties in vehicle attitude. In the Ship Relative GPS (SRGPS) aircraft landing application precision GPS phase measurements from multiple mast-mounted antennas are to be transferred to the landing deck touchdown point. A related requirement is transfer of phase data between antennas at various locations for integrity monitoring and signal combining purposes. Ideally, the errors introduced in the transfer process are substantially smaller than the errors in the measurements being transferred. A figure of merit is the ratio of transfer errors to single-epoch position-domain errors: the coordinate transfer error ratio (CTER). A transfer system is developed incorporating the flexure linkages in a network of up to three GPS-IMU pairs. In evaluating the performance of the system the CTER performance index is developed. In support of system architecture studies and refinement of the transfer system, a SRGPS simulation environment including network flexures between all components as well as GPS and IMU observable generation is also developed. Utilizing flexure estimates derived from the shipboard data the flexure dynamics parameters of the SRGPS simulation environment are adjusted for improved simulator realism. Simulations are then carried out for transfer scenarios involving transfer of yardarm observables to the flight deck. The results from these simulations show that even with substantially degraded single-epoch data on the yardarm to flight deck path, as might be caused by poor reception at the flight deck antenna, the CTER is on the order of 0.3, indicating small effect upon the yardarm measurements being transferred.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1277 - 1287
Cite this article:	Ahn, In Soo, Breslau, Ray, Sennott, Jim, "Development and Evaluation of a Precision Coordinate Transfer System for SRGPS," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1277-1287.
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