Comparison of Different Terrain Referenced Navigation Techniques

Jürgen Metzger, Jan Wendel and Gert F. Trommer

Abstract:	This paper presents the principles of three Terrain Referenced Navigation (TRN) techniques. These techniques will be compared and advantages and disadvantages will be pointed out. • The first technique is based on an extended Kalman filter (EKF) with an adapted measurement model. In the estimation step of the EKF a position update is calculated from a terrain height measurement and a digital map. This map is considered as a non-linear measurement function, describing the measurement model of the EKF. • A correlator is the basic principle leading to the second technique. Evaluation of correlation between a set of terrain height measurements and the corresponding set of data taken from a digital map provides a position estimate. • The third technique is based on a bayesian approach, which provides a position estimate by using a Bootstrap filter. This technique promises better results than the results of an EKF because Bootstrap filters are able to handle non-linear system and measurement models without the need of linearizing them. Also the restriction of Gaussian distributed probability density functions describing the state of a system is overcome. Algorithms based on these principles have been defined and implemented in a simulation-tool, developed at the Institute of Theory and Systems Optimization. Simulations of flights over terrain with different roughness, over maps with various resolutions, at different heights and with various initial position errors have been performed. This simulations are showing advantages of the Kalman filter and Bootstrap filter techniques in most circumstances. Only in an acquisition phase the Correlation technique can outperform its competitors. In most flight conditions the EKF technique gives slightly better results than Bootstrap filtering. On the other hand the advantage of Bootstrap filtering lies in the possibility to develop navigation filter and TRN separately.
Published in:	Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002) June 24 - 26, 2002 Hyatt Regency Hotel Albuquerque, NM
Pages:	132 - 141
Cite this article:	Metzger, Jürgen, Wendel, Jan, Trommer, Gert F., "Comparison of Different Terrain Referenced Navigation Techniques," Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002), Albuquerque, NM, June 2002, pp. 132-141.
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