GPS/INS Integrity Monitoring Using a Modified GPB1 Filter Bank

J. Wendel, O. Meister, R. Mönikes

Abstract:	Receiver autonomous integrity monitoring (RAIM) methods are widely used in GPS/INS systems in order to provide integrity for the navigation information. In order to identify and exclude a single faulty pseudorange measurement, snapshot RAIM algorithms require at least six satellites in view. While RAIM is a reasonable and proven solution for a stand-alone GPS receiver, it is obvious that in the case of a GPS/INS system, RAIM is a sub-optimal approach, as it does not use the information provided by the INS. One possibility to use the INS information for integrity monitoring purposes is an Interacting Multiple Model (IMM) filter bank, where each elemental filter assumes the pseudorange measurements belonging to one specific satellite to be disturbed. If the pseudorange measurements from one specific satellite are disturbed, the corresponding elemental filter will achieve a high probability, while the probabilities of the other filters processing the disturbed measurement as healthy decay towards zero. The major drawback of this approach is the computational load produced by the filter bank. In the new integrity monitoring approach proposed in this paper, the IMM filter bank is replaced by a Generalized Pseudo-Bayesian 1 (GPB1) filter bank. After the measurement processing, an IMM initializes each elemental filter for the following propagation step differently. In opposite to that, the GPB1 elemental filters are all initialized with the best estimate, which is obtained from the blending of the filter solutions taking into account their probabilities. In the special case considered here, the system models of all elemental filters are identical. Therefore due to the identical initialization, the propagation step of each elemental filter produces the same result. This allows to use one single filter in the propagation step instead of propagating state and covariance of each elemental filter separately, thereby reducing the computational load dramatically, allowing for a real-time implementation of the proposed algorithm. Numerical simulations illustrate that the performance of this new integrity monitoring approach is similar to the IMM-based integrity monitoring. Additionally, a reliable identification of faulty pseudorange measurements is possible with only five satellites in view, where the RAIM methods can only detect, but not identify, a fault.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1589 - 1595
Cite this article:	Wendel, J., Meister, O., Mönikes, R., "GPS/INS Integrity Monitoring Using a Modified GPB1 Filter Bank," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1589-1595.
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