Multipath Signal Simulation in a Dynamic Aircraft Landing Environment

Jan P. Weiss and Penina Axelrad

Abstract:	This paper presents code multipath analysis for two simulated aircraft landing scenarios. This work extends an existing simulation toolset that integrates 3D structure models, electromagnetic ray-tracing algorithms, antenna pattern measurements, and receiver tracking loop models to simulate code multipath errors. The first simulation includes only an F-18 aircraft to evaluate the effects of attitude dynamics on multipath produced by its structures. The simulation is run at a 10 Hz rate over the course of 3.8 hours, first without dynamics, and then with attitude dynamics modeled based on inertial navigation system data. The second simulation models the translational motions of an F-18 landing on an aircraft carrier. This environment model includes the aircraft, ship, and ocean surface. The multipath signals produced by each object are separately removed from the ray-tracing predictions to evaluate the contributions of multipath due to the ocean, aircraft carrier, and F-18 airframe to the total multipath error. Both scenarios demonstrate the utility of the multipath model for illuminating multipath properties that are not observable in experimental data. The first simulation reveals that rapid changes in multipath geometric delay induced by aircraft attitude motions lead to dominant high frequency multipath errors. Consequently, carrier smoothing of code measurements with a time constant of 20 sec reduces overall error statistics by 30-69%, compared to a reduction of less than 5% in the static case. The second simulation shows that multipath produced by the ship and ocean surface each contribute significantly to the total error below 30 deg and that multipath from the aircraft wings and tailfins causes almost all errors at higher elevations. The signal paths determined by the ray-tracing computations show that multipath due to the ship, while contributing to the low elevation error statistics, is only relevant when the aircraft is within ~200 m of the touchdown point. Multipath due to aircraft structures is generally small in magnitude because its geometric delay is less than 10 m.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	2687 - 2695
Cite this article:	Weiss, Jan P., Axelrad, Penina, "Multipath Signal Simulation in a Dynamic Aircraft Landing Environment," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 2687-2695.
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