Accuracy evaluation of UAS photogrammetry and structure from motion in 3D modeling and volumetric calculations

Abstract

Photogrammetric surveying using unmanned aerial systems (UAS) and structure from motion (SfM) is a rapidly emerging technique that has been widely used as a valuable research tool in geodesy and related disciplines. We studied surveying and three-dimensional (3D) modeling based on UAS and SfM. In particular, we focus on the accuracy and quality of UAS-SfM in 3D modeling and volumetric calculation of a building with an overhanging feature. For this purpose, two aerial surveys were performed using a fixed-wing and a multirotor aircraft with nadir and oblique camera axes. For validating the results, field surveys were carried out using terrestrial laser scanner (TLS), differential global navigation satellite system, and total station. To study the performance of SfM software on the accuracy and quality of point clouds, UAS images were processed using three software packages: Agisoft PhotoScan, Pix4Dmapper, and 3Dsurvey. As a result of photogrammetric image processing, 3D dense point clouds, mesh models, and digital surface models were generated. For validating the UAS-SfM results, the models were compared with the TLS model and field measurements; absolute accuracy assessments and model versus model comparisons were performed. The most accurate and high-quality 3D models comparable to TLS models were obtained from oblique images. PhotoScan generated relatively more accurate 3D models with the horizontal and vertical accuracy of root mean square error 0.025 and 0.02 m, respectively. The maximum discrepancies in dimensions and volume measurements from the UAS-SfM-derived point cloud were at the level of 0.01 m and 0.66 m 3 (0.03%). The results highlighted that using a lowcost UAS and SfM photogrammetry, high-accuracy and high-quality 3D models can be generated. The results confirm that with respect to its rapid data acquisition and centimeter-level accuracy, UAS-SfM can be considered as a suitable alternative approach to conventional measurement techniques, especially in engineering and emergency response.

Analysis and Precision of Light Detection and Ranging Sensors Integrated in Mobile Phones as a Framework for Registration of Ground Control Points for Unmanned Aerial Vehicles in the Scanning Technique for Building Information Modelling in Archaeological Sites

“…According to studies carried out in other works, remote sensing-based image capture (SfM) using remote sensing is reaching great popularity in the characterisation of landscapes with centimetre-level precision. For example, in landslide studies [43] (where it was shown that the use of multi-rotor UAVs improves the point cloud by 16% compared to the use of fixed-wing UAVs) or in the heritage preservation field [44] (in a study on a Monastery, the quality parameters of the point cloud were evaluated using what the author calls the Remotely Piloted Aircraft System (RPAS) and the TLS). However, in the field of archaeology, there are studies [45] that only approach this investigation using SfM without UAV.…”