Navigation and Seamanship (1+1)

3.1.8.5. Installation and maintenance of echosounders

Positioning and installation of the transducer are often decisive in ensuring proper performance. Normally the transducer should be placed between one third and one half of the vessel length from the bow and approx. one metre away from the keel. In vessels smaller than 30m the transducer may be closer to the keel. Noise may considerably reduce the efficiency of echo sounding and it is therefore of the greatest importance to avoid or reduce noise as far as possible. The ideal position of the transducer is at the deepest and at the same time most noise free point of the vessel. This point may be difficult to determine since the propeller noise and the noise produced by the flow of water along the hull may vary with the trim and the speed of the vessel fix the transducer well away from the propeller and rudder.

Transducer is usually housed in a streamlined ‘shoe’ or blister to reduce water noise and turbulence angle between 5^o and 8^o will vary according to the form of the low and the distance from it. The surface of the transducer should always be tilted 2^o forward in order to prevent turbulence on the transducer itself while underway. The tilting also has the effect of “shadowing” the transducer face from the propeller noise.