In this study, we conducted an on-site experiment on existing underwater drones, 3D data, etc. to examine the applicability of them and to identify issues that must be addressed, with the aim of developing an efficient and effective inspection method for the underwater components of marine structures.

As underwater components of structures are generally covered by marine creatures, we found it difficult to visually check the condition of components only with the underwater drone. However, we found it possible to apply the underwater drone for the preliminary inspection, which is to determine the area where to perform detailed inspections such as the thickness measurement of steel pipe piles. Therefore, underwater drones might contribute to the labor-saving and effective inspection and diagnosis.

We captured serial images on a steel pipe pile but were unable to generate a 3D model from images within the scope of this experiment. Possible causes of this failure might be the less distinctive features acquired from each image, the murkiness and floating objects in the water that prohibited us from acquiring clear images, and the waves and tidal currents that constantly shook the underwater drone and prevented it from capturing images stably.