Speed Log

Speed Logs are available in two forms to assist with measurement of ship speed: Doppler log – An acoustic speed log based on the Doppler effect in which the wave lengths of moving objects appear to shift in relation to the observer. This shift can be converted to speed, thereby giving a very accurate result.

Electromagnetic log – The electromagnetic log works by generating a small alternating current in a transducer producing an electromagnetic field in the adjacent water. As the vessel moves through the water, the voltage proportional to the speed is generated at 90 deg to the direction of travel.