JPALS: Scattering Model for Aircraft Carrier Multipath Errors

Preston Geren and Tim Murphy

Abstract:	The JPALS program is developing DGPS landing aids for carrier landings. One of the main concerns is the impact of multipath on system accuracy, continuity and availability. In order to scope the impact of the multipath component due to the aircraft carrier environment, a study was conducted using a physics-based discrete scatterer model for Fixed Radiation Pattern Antenna GPS antennas mounted on the topmost yardarm. Twelve scatterers were modeled for the respective antennas on each half of the yardarm, and ocean/deck ground bounce was included as well. Scatterer positions were determined from ship drawings, with scattering amplitudes obtained by a Fourier analysis method applied to test data collected from a representative location on an aircraft carrier. This paper describes the analysis and shows the resulting model predictions for multipath errors. The model predictions are then used to derive statistical models for multipath error magnitudes that can be used in JPALs system performance simulations. The motivation for this approach was twofold: first, the use of a higher-resolution physical model of the aircraft carrier was impractical due to budget and schedule constraints and second, the resulting model is assured to give realistic predictions of multipath error characteristics since observed multipath data obtained in a representative environment are used directly to develop the model. The results produced by the discrete scatterer model were compared to independent calculations from the University of Colorado and found to be in good agreement. The implications of this method for future multipath modeling are discussed in the conclusions.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	337 - 353
Cite this article:	Geren, Preston, Murphy, Tim, "JPALS: Scattering Model for Aircraft Carrier Multipath Errors," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 337-353.
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