Simple underwater monitoring of shallow water using a spherical camera mounted on a radio-controlled boat

During underwater monitoring observations in shallow water for coastal environmental conservation, the sea is not always clear and waves and current make the observational situation difficult. Underwater monitoring is still conducted mainly by human divers. Therefore, underwater robotics or remotely operated underwater vehicles (ROVs) that can monitor from a human diver's perspective are considered as labor-saving equipment. In this study, simple underwater monitoring equipment is developed using a radio-controlled (RC) boat in which a spherical camera is mounted for monitoring underwater conditions at relatively low costs. One purpose of this simple monitoring system is to obtain 360° images for observing sea beds and schools of fish without focus control. To develop the proposed simple monitoring system at a low cost, a commercially marketed spherical camera packed into a waterproof mobile-phone case is mounted on a twin-hulled RC boat. The images obtained include distortions caused by changes in the refractive index. A simple image correction based on a barrel-type image distortion method is provided. Additionally, some demonstrative experiments that were conducted in water tanks of aquariums and in a coastal channel are discussed.