“…Unless the matrix is sparse or has a specific structure that eases the computation, O(N 3 ) floating points operations would be required for any matrix inversion. Approaches for modeling large covariance matrices in purely spatial settings include low rank and covariance tapering models [21,4,13, and references therein] and multivariate tapering proposed in Bevilacqua et al [7], approximations using Gaussian Markov Random Fields (GMRF), the Laplace transform and Stochastic Partial differential Equations [35,36,29,9,8], products of lower dimensional conditional densities [see 15,16, and references therein] and composite likelihoods [17] with the recent multivariate extension proposed in Bevilacqua et al [6]. A large number of extensions to spatio-temporal settings have been proposed, including [14], [20] and [27] who introduce dynamic spatio-temporal low-rank spatial processes, while [39] choose a GMRF approach.…”