Aerial photogrammetry and three-dimensional modeling of the Tottori Sand Dunes using UAV

Abstract

The Tottori Sand Dunes, located along the Sanin Coast of Japan, are a UNESCO Global Geopark and popular tourist attraction with millions of visitors every year. Monitoring of environmental conditions is needed for protection and utilization of the dunes. We investigated three-dimensional (3D) modeling by UAV (Unmanned Aerial Vehicle: Drone) for cost- and time-efficient environmental monitoring of the dunes. The objectives of this paper were (i) aerial photogrammetry and 3D modeling of the dunes using UAV, and (ii) validation and evaluation of the 3D models. 1682 vertical photographs (side overlap: 60%, and top-bottom overlap: 80%) were taken at altitudes of approximately 100 m above ground level using an UAV (Phantom3 professional, DJI) for a 1500 m² area of the dunes. The obtained images were processed using SfM software (PhotoScan Professional, Agisoft) for building 3D models. The position data of survey piles in the dunes were used as the GCP (ground control point) setting for image processing and model evaluation. We were able to build high-resolution 3D models with colorful texture that enable environmental monitoring of the dunes. Reasonably accurate models were built when a large number of survey piles were used as GCPs during processing. Accuracy of the models was further improved when only a small number of GCPs were used for modeling by (i) excluding inappropriate GCPs, (ii) setting GCPs for large areas, and (iii) adding a center point as a GCP.