Covariance Estimation for Terrain Referenced Navigation with a Comparison Technique

J. Metzger, O. Meister, G.F. Trommer, F. Tumbrägel and B. Taddiken

Abstract:	This paper deals with a Terrain Referenced Navigation (TRN) system providing position information and estimations of the corresponding covariance matrices. The investigated comparison technique does not automatically provide a covariance matrix of the estimation error as for example Kalman filter techniques do. A possibility to estimate this covariance is to calculate a moving average and a moving covariance using the difference between the position hypotheses and the position fix of the TRN module. Due to changing terrain roughness, different flight situations, and different radar noise the covariance is changing rapidly over time and the deserved calculation of the covariance will not always give proper results. Therefore, this paper introduces a new way of calculating the expected covariance of the position fixes. Information about the noise of the terrain height measurement and the terrain characteristic in the search area are used to determine the covariance. This leads to a non-linear connection between the standard deviation of the measurement, the estimated cross-correlation of the terrain, and the covariance of the position error. Simulation results of the common covariance estimation using the moving variance and the new method show a considerable improvement of the estimated position error. Even in extremely flat terrain the estimated covariance covers the generated false fixes and allows a proper processing in a central navigation filter. Another improvement is the ability to respond promptly on changing terrain. This leads to a increased navigation performance of the central navigation system that can rely on the position fixes and covariances of the Terrain Referenced Navigation system.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	571 - 580
Cite this article:	Metzger, J., Meister, O., Trommer, G.F., Tumbrägel, F., Taddiken, B., "Covariance Estimation for Terrain Referenced Navigation with a Comparison Technique," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 571-580.
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