Unmanned aerial vehicles (UAV) as a support to visual inspections of concrete dams

Some signals of deterioration and cracking of dams can only be identified by visual inspections. For this reason, visual inspections are irreplaceable in the control of the safety of dams. Concerning the exterior walls, and sometimes also the crest, as there is no direct access to most of these areas, it is used cameras and/or binoculars to perform the inspection work, which is usually done from the banks of the river. In the last few years it has appeared new aerial mini aircrafts – airplanes and helicopters and multirotors, remotely piloted, commonly called drones – that can carry digital cameras and can be flown near to the structures. For this reason they can acquire high quality images, at a very low price, from points of view that were never used before. This paper presents the results of a photographic survey of a small area on the downstream face and of the central spillway of Bouçã dam, in Portugal. The photographs were taken by a digital camera mounted under a octocopter drone. Besides the interest of the photographs, since one can easily see all the features of the surface of the dam, the images were gathered and it was created an orthomosaic from the area surveyed on downstream face, a cartographic product that can be used as a support to other photographic surveys, and a point cloud of the spillway.