For example, information on when and where the target organism has
been is essential for understanding its movement and behavior.
In addition, when we observe under the water from a ship with observation
equipment, it is important for the equipment to know where the observation
target is, even if it is not a direct observation target.
Although GPS can obtain location information on land or the water
surface, it cannot be used for underwater positioning because radio waves do
not reach far underwater. Therefore, sound waves are used as a means to identify
the position of an object in the water.
