Automatic Matching Based on Dynamic Threshold in Close-Range Photogrammetry

Points matching is a key technology in close-range photogrammetry. The epipolar line constraint that confines the research area from two dimensions to one dimension, can improve the efficiency of matching process. In the paper, coded targets are applied to get a set of accurate correspondences of points between images, and then the correspondence set is used for calculating fundamental matrices by normalized 8-points algorithm that can be implemented quickly and simply. Because of the ambiguities, a completely accurate correspondence set will not be gained only by epipolar line constraint, and other technologies should be combined with epipolar line constraint. Three views are used to decrease ambiguities, and a method of dynamic threshold is presented to reject wrong correspondences. A proper threshold is calculated, and those correspondences whose corresponding distance is larger than the dynamic threshold, are considered as wrong matching points. Many experiments show that the correct rate of matching is about 99.98%, which means an automatic, efficient, accurate matching process can be implemented by the methods in this paper.