Directional Echo-sounding

A description is given of sea trials of two types of narrow-beam echo-sounder developed with a view to obtaining information as regards both the depth and the slope of the seabed. One system involves a two-channel interferometric arrangement, which provides a family of several spaced receiving beams; the other uses an eight-element hydrophone array with electronic sector-scanning of the resultant narrow beam. Photographs of typical displays show that comparable values may be derived for the slope of the seabed beneath the ship for both systems in simple situations. Difficulties in interpretation of the interferometer record with more complex slopes render the use of the electronically-scanned system advisable in such circumstances.