Keypoint matching by outlier pruning with consensus constraint

A simple and reliable keypoint matching method is proposed in this paper. Our research is motivated by the desire to improve the performance of multi-view geometry (MVG) based verification in visual loop closure detection under significant illumination change, where traditional methods may fail due to their inability to either find a sufficient number of correctly matched keypoints or identify correct underlying camera motion to verify the matches. Our method is inspired by research on the spatial statistics of optical flow. By observing that the displacement of matching keypoints between a pair of images is equivalent to the optical flow under the assumption of small camera motion (which is true in applications such as loop closure detection), we exploit the fact that the displacement of correctly matched keypoints between two images must follow a well-defined distribution. This paves the way to a keypoint matching method that uses this distribution to screen or prune potential matching keypoints, so as to remove the incorrect matches (outliers) and retain the true matches (inliers) without being overly and solely dependent on keypoint descriptors. The proposed method is validated on the outdoor image sequences and shows superior performance to the standard keypoint matching method based on distance ratio test.