Using Orthophoto for Building Boundary Sharpening in the Digital Surface Model
This work addresses a specific issue in 3D urban reconstruction for applications like mapping and planning, but it is incremental as it builds on existing stereo matching methods.
The paper tackles the problem of depth discontinuities being smoothed in Digital Surface Models generated by semi-global matching stereo algorithms, particularly in urban areas like fences or narrow streets, by using orthophoto line segments to sharpen building boundaries, with experimental results demonstrating robustness and effectiveness on satellite datasets.
Nowadays dense stereo matching has become one of the dominant tools in 3D reconstruction of urban regions for its low cost and high flexibility in generating dense 3D points. However, state-of-the-art stereo matching algorithms usually apply a semi-global matching (SGM) strategy. This strategy normally assumes the surface geometry pieceswise planar, where a smooth penalty is imposed to deal with non-texture or repeating-texture areas. This on one hand, generates much smooth surface models, while on the other hand, may partially leads to smoothing on depth discontinuities, particularly for fence-shaped regions or densely built areas with narrow streets. To solve this problem, in this work, we propose to use the line segment information extracted from the corresponding orthophoto as a pose-processing tool to sharpen the building boundary of the Digital Surface Model (DSM) generated by SGM. Two methods which are based on graph-cut and plane fitting are proposed and compared. Experimental results on several satellite datasets with ground truth show the robustness and effectiveness of the proposed DSM sharpening method.