Monocular SLAM as a Graph of Coalesced Observations

We present a monocular SLAM system that avoids inconsistency by coalescing observations into independent local coordinate frames, building a graph of the local frames, and optimizing the resulting graph. We choose coordinates that minimize the nonlinearity of the updates in the nodes, and suggest a heuristic measure of such nonlinearity, using it to guide our traversal of the graph. The system operates in real-time on sequences with several hundreds of landmarks while performing global graph optimization, yielding accurate and nearly consistent estimation relative to offline bundle adjustment, and considerably better consistency than EKF SLAM and FastSLAM.