Generating of a three-dimensional terrain model with unmanned aerial vehicles and usage opportunities in forest road project (Bolu sample)

In this study, three-dimensional Digital Terrain Models (DTMs) were generated from high-resolution images acquired by Unmanned Aerial Vehicles (UAVs), and the potential use of these models in the forest road design process was investigated. The study area is a 300 m long forest road alignment located within the boundaries of the Göynük Forest Enterprise, Bolu Regional Directorate of Forestry. A DJI Phantom 4 Pro RTK was employed to conduct two separate flights in 2019 (before construction) and 2025 (after construction). The collected images were processed in Pix4D Mapper to produce orthophotos, dense point clouds, Digital Surface Models (DSMs), and DTMs. The resulting datasets were analyzed in ArcGIS 10.3, transferred to AutoCAD Civil 3D, and the road design process was carried out in accordance with the standards of the General Directorate of Forestry. The findings demonstrate that UAV-based photogrammetry provides highly accurate data within a short time. Analysis of the DTMs revealed a total excavation volume of 1021.21 m³ and a fill volume of 980.74 m³, with approximately 40.47 m³ of excess excavation. These results indicate that the constructed road complies with the standards of a Type-B secondary forest road. Furthermore, the integration of GIS and CAD facilitated a faster, more cost-effective, and environmentally sustainable alignment design. The UAV-supported terrain modeling approach offers more precise and efficient results compared to traditional methods and constitutes an important alternative for natural resource management and sustainable forest road planning.