| Summary: | 碩士 === 國立成功大學 === 測量及空間資訊學系碩博士班 === 96 === Lidar (Laser Scanner) is capable of collecting a large number of 3D points, in which abundant surface features are implied in the distribution of point cloud data. However, these surface features should be extracted to from explicit information, i.e., it is necessary to transfer the point cloud data into mathematical expressions or vector data descriptions.
The proposed algorithm of surface reconstruction is based on the schemes of surface growing and surface feature fitting. It merges the co-plan points and extracts surface features from point cloud data. There are two factors to conduct the growing process: the angle between two normal vectors of adjacent patches and the distance of the point from the growing surface. Every merged cell is considered as a small patch, then the connect areas by region growing regarded as a surface feature. The reconstructive surface features in the proposed method includes planar features, spherical features, cylindrical features, and polynomial surface features.
The experimental data include ground-based Lidar and airborne Lidar. The overall results show the successful application examples of the proposed algorithm. In the experiment, the initial parameters such as grid sizes, threshold of angle, threshold of distance and the growing seed position are also discussed and extracted from point cloud data using a semi- automatic method. The results of reconstructive surface provide points cluster with the same surface characteristics and fitting parameter of the surface features. The extracted surface features will be useful for 3D modeling.
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