Abstract
Epipolar rectification is of great importance for 3D modeling by using UAV (Unmanned Aerial Vehicle) images; however, the existing methods seldom consider the perspective distortion relative to surface planes. Therefore, an algorithm for the rectification of oblique images is proposed and implemented in detail. The basic principle is to minimize the rectified images’ perspective distortion relative to the reference planes. First, this minimization problem is formulated as a cost function that is constructed by the tangent value of angle deformation; second, it provides a great deal of flexibility on using different reference planes, such as roofs and the façades of buildings, to generate rectified images. Furthermore, a reasonable scale is acquired according to the dihedral angle between the rectified image plane and the original image plane. The low-quality regions of oblique images are cropped out according to the distortion size. Experimental results revealed that the proposed rectification method can result in improved matching precision (Semi-global dense matching). The matching precision is increased by about 30% for roofs and increased by just 1% for façades, while the façades are not parallel to the baseline. In another designed experiment, the selected façades are parallel to the baseline, the matching precision has a great improvement for façades, by an average of 22%. This fully proves our proposed algorithm that elimination of perspective distortion on rectified images can significantly improve the accuracy of dense matching.
Highlights
Aerial oblique imagery has become an important source for acquiring information about urban areas because of their visualization, high efficiency and wide application in domains such as 3D modeling, large-scale mapping and emergency relief planning
The horizontally rectified image generates more points than the vertical rectification and commonly used rectification for the roofs
A new rectification algorithm for aerial oblique images is proposed that minimizes the distortion of surface planes
Summary
Aerial oblique imagery has become an important source for acquiring information about urban areas because of their visualization, high efficiency and wide application in domains such as 3D modeling, large-scale mapping and emergency relief planning. This method is relatively complex and requires large numbers of calculations in three-dimensional space Another non-linear transformation method expressed in a paper by [10] proposes an accurate computation method based on rectification of spherical-camera images via resampling the same longitude line. Unlike the methods described above, which reduce distortion by explicitly minimizing an empirical tangent value of angle deformation This manner, the rectified images will have by smallest perspective measure, the proposed approach is toInminimize a cost function that is constructed the tangent value distortion for some surface planes and features can be matched quite accurately by correlation. The rectified images will have smallest perspective distortion addition, the homography based method yield very large images orbycannot rectify at These for some surface planes and features canmay be matched quite accurately correlation.
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