UAV-Based Methodology for Photogrammetric Survey Applied to the Analysis of High Mountain Hydrographic Basins: Case Study of Ecuador

Worldwide photogrammetric studies have had a great impact in relation to environmental studies of hydrology; however, at Ecuadorian context this technique level has been little experienced due to the lack of knowledge or the little insertion of this technology type. Ecuador, being a country that is part of the Andes Mountain range, is characterized by having great mountainous relief and having high mountain hydrographic basins. In this context, the Ecuadorian Andean territory, with its irregular elevations and slopes, represents an adequate scenario to carry out photogrammetric studies and retrieve information for different types of environmental studies. Our work consists of developing an applicable and replicable study methodology for this area, using unmanned aerial vehicles (UAV). This methodology is based on own experiences generated in a photogrammetric study of Yanuncay river basin, located in the Cuenca Canton, Azuay Province. The processes followed for photogrammetric survey are detailed, considering the area topology and the areas of interest accessibility. The photographs were taken with a “DJI Phantom 4 Pro+” and processed to obtain a highly accurate orthophoto and digital elevation model (DEM). Subsequently, the information obtained was analyzed using ArcGIS, comparing the results with a previous study of the same area, but using satellite images. The study variables focus on the geomorphology and physical aspects of basins. Results show that the photogrammetric survey higher resolution allows a more accurate analysis, recovering information that satellite images cannot generate due to the complicated mountainous profile and that is important in the context of environmental conservation and flood prevention.