3D modelling and visualization of large building using photogrammetric approach
The progress in modern technologies such as precise lightweight cameras mounted on unmanned aerial vehicles (UAV) and the more user-friendly software in the photogrammetric field allows for 3D model construction of any structure or shape. Software now achieves in sequence the processes of matching, generating tie points and block bundle adjustment and generating digital elevation models. The aim of this study is to make a virtual 3D model of the College of Engineering, University of Duhok, Kurdistan Region, Iraq. The data input is vertical and oblique imagery acquired by UAV, with the ground control points being distributed on the surrounded ground, facades, and roof. Ground control points were measured by the GPS RTK system in addition to the reflectorless total station instrument. The data is processed mainly using Agisoft PhotoScan software as well as the Global Mapper and the ReCap software. The output is a 3D model, digital elevation model, and orthomosaic. Geometric and visual inspections were carried out. Some imperfections appeared on the sharp edges and parapets of the building. In the geometric accuracy of selected points on the building, the maximum standard deviation in the coordinates was ±4cm. The relative accuracy in distance measurements was in the range from 0.72% to 4.92 %.