Effects of Ship`s Roll Motion on the Detectable Area of Echo Sounder

선체의 횡요와 어군탐지기의 탐지기능범위에 관하여

When detecting underwater targets using echo sounder, the echo signals varies with the angular displacement of the transducer due to ship's motion. Then, the effect of the angular which effects the capability of the echo sounder must be investigated in relation to the detection of fish concentration, particularly, the abundance estimation of fish. In this pater, as the basic research to investigate the effect of the ship's motion when estimating the fish stocks by acoustic methods, the authors was theoritically considered the variations in the values of the two way directivity function of transducer in the direction of the targets which caused by the angular motion of transducer. Here, the effects of the movement of target and ship's running are neglected. At the same time, the data was applied to estimate the angular shift of the detectable area of echo sounder due to transducer displacement. From the results analyzed, we found that the angular shift of the detectable area due to ship's motion increases both as the roll angle increases and as the beamwidth becomes narrower, varies with the depth.