Research on digital modeling of ancient building appearances based on UAV three-dimensional reconstruction

Abstract

A digital exterior-modeling method based on unmanned aerial vehicle (UAV) oblique photogrammetry and point cloud processing is proposed. The difficulty encountered by conventional surveying methods in comprehensively acquiring spatial information from elevated and occluded areas of historic buildings is addressed by this method. The Jiuyun Fangding monument was selected as the study object. Images were acquired using a multi-altitude, multi-angle, layered circumferential flight strategy. A three-dimensional (3D) model was then reconstructed through feature matching, camera-pose estimation, multi-view stereo matching, point cloud registration, and texture mapping. Four representative dimensions were selected, and the measurements obtained from the reconstructed model were compared with field measurements. The results indicated that: (1) the absolute errors of the four dimensions ranged from 0.006 to 0.039 m, with the maximum spacing between the load-bearing columns exhibiting the largest absolute error of 0.039 m; (2) the relative errors ranged from 0.63% to 1.81%, with the width of the load-bearing column exhibiting the largest relative error of 1.81%; and (3) the reconstructed model provided a relatively complete representation of the overall architectural form and the principal structural components. The proposed method can therefore provide technical support for the digital documentation, 3D visualization, and dimensional verification of historic buildings.