Automatic Deformation Extraction Method of Buildings in Mining Areas Based on TLS Point Clouds

Presently, the deformation extraction of buildings in mining areas using terrestrial laser scanner (TLS) point clouds is performed manually. Automatic deformation extraction holds great significance for building deformation monitoring in mining areas. Therefore, this study proposes an automatic extraction method for building deformation in mining areas using TLS point clouds. The corner points of doors and windows on the wall are considered as key points and the wall deformation in the mining area is extracted with minimal manual intervention. First, the input data were preprocessed, including 2D boundary point cloud acquisition and denoising (using a distance slope filter). Next, the key points were extracted via three steps: boundary line splitting, seed key point clustering, and key point judgment. Finally, the 3D coordinates of the key points and the relationship between the key points of the two phases were established to calculate the deformation value. The results confirmed negligible difference between the deformation value extracted using this method and the real value. Most of the errors were between −5 and 5 mm, and only a few exceeded ±5 mm; however, no error exceeded ±9 mm. The deformation value obtained using this method was almost identical to that obtained using the manual method, and the absolute error between them was below 8 mm. The performance verification of this method showed that the proposed distance slope filter removed the noise points more effectively compared to that of the traditional denoising filters, i.e., statistical and radius filters, establishing its suitability for the complex measurement environment of mining areas. During the automatic extraction of key point coordinates, the root mean square error (RMSE) values were below 2.0 mm; RMSE values during manual extraction were below 7.1 mm. The proposed method demonstrated greater stability than that of the manual extraction method.