An UAV for 3D Tree Surveying Method as an Improvement for Dam Construction Environmental Impact Manifestation in Mexico

Abstract. In Mexico, dam construction requires a thorough Environmental Impact Manifestation (Manifestación de Impacto Ambiental, or MIA), which is a comprehensive environmental assessment report submitted to the Secretariat of the Environment and Natural Resources (SEMARNAT) for review and authorization. The MIA, however, is a formal document that outlines the potential environmental impacts of a dam project, including construction and operation. These methodologies are obsolete compared to the currently available technologies. This study tests a new procedure of 3D tree surveying of a closed-canopy woodland of different types of forests on a dam in Linares, in eastern Mexico. A DJI drone—Matrice 350 assembly—was used to collect imagery in 16 missions during the summer of 2024. A canopy height model was built from the UAV-extracted point cloud and LiDAR bare earth surface. Treetops were delineated in a variable-sized local maxima filter, and tree crowns were outlined via inverted watershed segmentation. The outputs include a tree inventory that contains thousands of trees (location, tree height, crown polygon), varying among the different types of vegetation. These new datasets give a more comprehensive approach to establish further decision making.