Generic factor-based node marginalization and edge sparsification for pose-graph SLAM

This paper reports on a factor-based method for node marginalization in simultaneous localization and mapping (SLAM) pose-graphs. Node marginalization in a pose-graph induces fill-in and leads to computational challenges in performing inference. The proposed method is able to produce a new set of constraints over the elimination clique that can represent either the true marginalization, or a sparse approximation of the true marginalization using a Chow-Liu tree. The proposed algorithm improves upon existing methods in two key ways: First, it is not limited to strictly full-state relative-pose constraints and works equally well with other low-rank constraints such as those produced by monocular vision. Second, the new factors are produced in a way that accounts for measurement correlation, a problem ignored in other methods that rely upon measurement composition. We evaluate the proposed method over several real-world SLAM graphs and show that it outperforms other state-of-the-art methods in terms of Kullback-Leibler divergence.