Quarterdeck (6.3) Online -- Texas A&M Oceanography

Texas A&M University
Department of Oceanography

Winter 1998 / Spring 1999 - Vol. 6, No. 3

The echo sounder

ACTIVITY:

Can you make a profile from this actual echo sounding data from an area near Iceland? Then graph the seafloor using your own graph paper.

What really opened scientists' eyes to the deeps was the invention of the echo sounder. Originally developed to detect enemy submarines before World War II, the echo sounder is just sonar (an acronym for "sound navigation and ranging") put to geologic use.

Here's how it works: A transducer, typically on the bottom of the ship's hull, emits a short sound pulse. The pulse travels downward, strikes the seafloor, and returns to the transducer. The echo sounder times the return of that signal from the ocean bottom. Because we know the speed of sound in water (usually 1,500 meters per second), that round-trip time can be used to calculate depth.

With the echo sounder, scientists can measure the ocean's depth in a matter of seconds while the ship is moving -- an improvement on the ropes and weights technique, which took hours stopped in the ocean. The echo sounder enabled ships to routinely make thousands of depth measurements while crossing the oceans, and it became possible to make modern bathymetry (ocean depth) charts. Many ships carry echo sounders, or precision depth recorders, that instantly display the depth of the sea on a computer screen. In fact, you can buy one of these at the local hardware store for finding fish at the lake.

Like most ships, Texas A&M's research vessel, the R/V Gyre, is equipped with echo sounding devices. Captain Dana Dyer (above, at the helm of the Gyre) uses the echo sounder to ensure that water beneath the keel is deep enough for the ship.

http://oceanography.tamu.edu/Quarterdeck/1998/3/sager-2.html
Copyright 1998-1999, Department of Oceanography, Texas A&M University.
Updated November 24, 1998. (abdw)

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