Abstract
Line matching is the foundation of three-dimensional (3D) outline reconstruction for city buildings in aerial photogrammetry. Many existing studies have good line matching effects when dealing with aerial images with short baselines and small viewing angles. However, when faced with wide-baseline and large viewing-angle images, the matching effect drops sharply or even fails altogether. This paper deals with an efficient and simple method to achieve better line matching performance by a pair of wide-baseline aerial images, which make use of viewpoint-in variance to conduct line matching in rectified image spaces. Firstly, the perspective transformation relationship between the image plane and the geoid plane can be established from a Positioning and Orientation System (POS). Then, according to perspective projection matrices, two original images are separately rectified to conformal images, whose perspective deformation of large viewing-angle can be eliminated. Finally, the rectified images are used to conduct line matching, and the matched line segments obtained are back-projected to the original images. Four pairs of urban oblique aerial images are used to demonstrate the validity and efficiency of this method. Compared with line matching on original images, the number and the correctness of the matched line segments are greatly improved. Moreover, there is no loss of time efficiency. The proposed method can also be applied to general UAV (Unmanned Aerial Vehicle) aerial photogrammetry and introduced into matching for other geometric features, such as points, circles, curves, etc.
Highlights
Oblique photogrammetry is a newly developed technology that can effectively create a three-dimensional (3D) model of a city’s buildings
This paper proposes an improved method for the line matching of wide-baseline images based on viewpoint-invariance
Perspective transformation matrices are established using the exterior orientation elements provided by Positioning and Orientation System (POS) and the original images are rectified into conformal images
Summary
Oblique photogrammetry is a newly developed technology that can effectively create a three-dimensional (3D) model of a city’s buildings. Compared with conventional aerial images, oblique images have their own processing challenges, especially feature matching, due to their wide baselines and large viewing angles. Many scholars have conducted research on point matching for oblique images and achieved reasonable results. Affine scale-invariant feature transform (ASIFT) simulates a series of changes in viewing angle and obtains more matched points in the case of a wide baseline [1]; Xiao et al used a positioning and orientation system (POS) to obtain attitude angles. Sci. 2018, 8, 938 in order to establish affine invariance and to achieve the matching of oblique images [2]; the method proposed by Tuytelaars et al is based on matching local affine invariant regions, which provides good results for matching under wide-baseline conditions [3]. The characteristics of the line and point are quite different, and processing of the line feature is more complex than the point
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