Geological surveying prior to site selection is a crucial component to ensure the smooth implementation of large-scale infrastructure projects. To explore cost-effective and practical geological surveying techniques, a mining area in South Central China was taken as an example and unmanned aerial vehicles (UAVs) equipped with high-resolution cameras and with high-density grid imaging mode were utilized to capture images and achieve 3D reconstruction of the study area. After generating a digital elevation model from the point cloud model, relevant geological information was extracted to conduct preliminary assessment of potential geological risks. The results indicate that UAV-based aerial survey significantly improves the efficiency of geological surveying compared to manual techniques, providing a clear and accurate representation of the actual conditions in the test area. The high-density grid imaging mode proves to be convenient for this kind of missions, and the integrated analysis of 3D models, point cloud models, and DEM (digital elevation models) exhibits a strong correlation with reality. The findings of this study offer novel insights for geological reconnaissance practices.