Sounding 4
Sounding 4 : Taking a measurement of the depth of the water beneath a ship. A hand lead and line can be used in shallow water and soundings up to 20 fathoms (120 ft, 36. 6 m) can be taken. More sophisticated equipment such as an echo sounder can be used. These send sound impulses in the sea or river bed and the echoes are received back converted to electrical energy and indicated on and instrument in feet or metres
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