Using a fan-shaped acoustic beam (a wide beam in one direction and a narrow beam at right angles to it), a wide beam is used to detect the sending wave to the port and starboard sides of the ship, and a wide beam is used to detect the receiving wave in the forward and backward directions (mills-cross method). This method allows us to obtain detailed information on the seafloor in a very narrow area where the transmitting and receiving waves overlap, and to study the topography of the seafloor and sediments on the seafloor. The method is equipped with a function to compensate for ship sway and sound velocity, which enables a detailed picture of the situation to be obtained. The figure below shows an acoustic image of the wreck taken by the Training Ship Oshoro-Maru.
