“…Sparse local features [6-8, 13, 14, 19, 30, 32-34, 50, 55, 56,60,65] are a popular approach to correspondence estimation. These methods follow a detect-then-describe approach that first applies a feature detector [7,13,19,30,32,34,50,65] to identify a set of keypoints or interest points. The detector then provides image patches extracted around the keypoints to the following feature description stage [6-8, 14, 30, 33, 55, 56, 60, 65].…”