A UKF Based GPS/DR Positioning System for General Aviation

Dong An, Jose A. Rios and Darren Liccardo

Abstract:	This paper proposes an Unscented Kalman Filtering (UKF) based approach for a low cost seamless Global Positioning System/Dead Reckoning (GPS/DR) positioning system using information from multiple onboard sensors including a GPS receiver, AHRS (Attitude and Heading Reference System), remote magnetometer, airdata computer, and on-line World Magnetic Model (WMM). Traditionally, it is inconvenient to directly apply GPS pseudo range and delta range to a GPS Kalman filter or a GPS/DR filter in which latitude, longitude, and altitude are modeled as state variables. Instead, GPS position and velocity is solved in ECEF (Earth Centered Earth Fixed) coordinate frame using pseudo range and delta range measurements. AHRS and airdata are used to dead reckon for state propagation in between GPS updates. Wind speed error dominates in this DR approach. In this paper, a UKF is designed to directly use GPS raw pseudo range and delta range measurements to estimate both state and parameters of a nonlinear dynamic system model in which a local tangent navigation coordinate frame (NED, North, East, Down) is used. We are motivated by the need to track position with more tolerance to loss of GPS satellites than can be provided by a decoupled GPS receiver alone. We use a UKF over the traditional EKF (Extended Kalman Filter) to take advantage of its higher-order accuracy and mechanization simplicity. We include on-line estimation of parameters in our filter to gradually shape a wind vector model with GPS measurements. As a consequence, the robustness to uncertainty in the wind speed model is maximized. The simulation results demonstrate that the proposed system is capable of providing continuous position data to bridge GPS outages and can provide gracefully-degrading aiding information for an AHRS at higher rates than GPS alone.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	989 - 998
Cite this article:	An, Dong, Rios, Jose A., Liccardo, Darren, "A UKF Based GPS/DR Positioning System for General Aviation," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 989-998.
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