UAV Photogrammetry Application to the Monitoring of Rubble Mound Breakwaters

Monitoring of breakwaters is a key aspect to prevent failures that affect the safety and quality of service. Unmanned aerial vehicle (UAV) photogrammetry gives low-cost and accurate geometric data, flexibility, and productivity to perform aerial surveys, although the weather conditions restrict flights for wind speeds above 50 km/h (the Mikrokopter system). Despite the promising potential of these systems, its ability to monitor movement of cubes in breakwaters has not yet proven. The UAV photogrammetry is tested for the research reported in this paper in the Baiona breakwaters (northwestern Spain). A SD of 0.026 m is obtained from the point cloud. The detection limit of the system is evaluated and rotations lower than 1° could be detected. This value is calculated from the measurable differences in height values after the virtual rotation of a single cube. The system provides the exact position where the movement of the cube is produced and can be easily integrated with geographic information system–based management systems.