Simultaneous use of sideways-looking sonar, strata recorder and echo sounder

In geological survey, the simultaneous operation of these three equipments on one vessel can have considerable merit. The sideways-looking sonar (known as the `Transit Sonar¿) has a range of 600 yd and gives an approximately true plan of the sea bed on dry paper 6 in. wide when the ship moves at 5.7 (or 2.85) knots over the ground. The record produced by the `Transit Sonar¿ may be readily correlated with the corresponding Admiralty chart. The Strata Recorder operates at 9.6 kHz, at which frequency the acoustic waves penetrate the sea bed. Good resolution is obtained on dry paper due to the use of short pulses and relatively narrow acoustic beams. A special circuit gives time-varied gain, triggered by the sea-bed echo, to employ the dynamic range of the paper in the optimum way. The precision echo sounder records on dry paper 10 in. wide. The capacitor- discharge transmissions at 32 kHz are switched by a silicon controlled rectifier. The position of the survey vessel at any instant may be obtained from a radio position-fixing system or by visual fixes. Some examples of interesting sea-bed features are portrayed in the figures, each a combination of the simultaneous records correlated in time on the same scale, together with their geological and topographical interpretations. Sand waves of wavelength 13 ft (4 m) and as little as 9 in. (23 cm) high have been resolved quite readily