Modelling farmland topography for suitable site selection of dam construction using unmanned aerial vehicle (UAV) photogrammetry

UAV photogrammetry and 3D mapping are gaining fast and wide applications around the world majorly due to the relatively low-cost advantage it offers in the acquisition of high resolution 3D topographic models when compared to LiDAR. This research seeks to demonstrate the applicability of UAV photogrammetry and Geographic Information System (GIS) in modelling the topography of a farm land located in Kwandere community, Lafia, Nasarawa state, Nigeria, for the selection of a suitable site for the construction of an earth-fill dam. The image data was acquired with the aid of a DJI Phantom 2 UAV at 120 m flying height, with a 3.61 mm camera focal length and at 65% overlap. The acquired images were processed using Agisoft Photoscan digital photogrammetric software and 20 GCPs were used for the georeferencing and check points for accuracy assessment. The Digital Elevation Model (DEM) of the area was generated from the acquired 2D image sequences using Structure from Motion (SfM) techniques, at a horizontal and vertical accuracy that falls within the desirable threshold according to NSSDA standard. Using the hydrologic tool of ArcGIS 10.3.1, the produced DEM together with the contour map of the area was finally used to determine the suitable location for the siting of dam using topographic constraints. The results obtained demonstrate the robustness of UAS products and their usefulness for planning purposes in construction and engineering applications.