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Contents

1962: Vol. XXXIX, No. 1

Interpretation of Echo Sounding Profiles

  • Dale C. Krause
Submitted
July 26, 2018
Published
2018-03-23

Abstract

Modern echo sounders and detailed bathymetric surveying have demonstrated the need for the theoretical treatment of echo traces that would be expected from geometrical features on the sea flor, thereby giving an insight into the interpretation of the true feature. The two basic features that govern the interpretation are (1) the relationship of the true and recorded sea floor slopes, respectively tan 0 and tan ç, shown by P. de Vanssay de Blavous (1933) : sin 9 = tan ç and (2) that any sharp projection above the sea floor gives a hyperbolic echo trace (Hoffman , 1957). Using these principles, the following figures are examined mathematically, both two-dimensionally and three-dimensionally as being representative of possible features on the sea floor : inclined plane, cone, hemisphere, hyperbola, and parabola. A semi-ellipse was analyzed two-dimensionally. Some depressions were analyzed also. In all except the parabola, hyperbolic echo traces were prominent, differing by differing constants. The parabola and the semi-ellipse also gave parabolic echo traces. Other features were examined but found to have echo traces with complex characters. Three complicating factors were examined. (1) The motion effect — the effect of the forward motion of the ship whereby the echo is not received where the sound pulse was emitted; (2) the correction due to sound velocity variation in the sea; and (3) the effect of the refraction of the sound ray due to the sound velocity variation. The first and last factors are shown to be negligible in general. Tables exist to correct for the second factor.