Covariance Intersection in state estimation of dynamical systems

The Covariance Intersection algorithm linearly combines estimates when the cross-correlations between their errors are unknown. It provides a fused estimate and an upper bound of the corresponding mean square error matrix. The weights of the linear combination are designed in order to minimise the upper bound. This paper analyses the optimal weights in relation to state estimation of dynamical systems. It is shown that the use of the optimal upper bound in a standard recursive filtering does not lead to optimal upper bounds in subsequent processing steps. Unlike the fusion under full knowledge, the fusion under unknown cross-correlations can fuse the same information differently, depending on the independent information that will be available in the future.