Texas A&M University
Department of Oceanography
Winter 1998 / Spring 1999 - Vol. 6, No. 3
Multibeam echo sounder
FACT:
A multibeam echo sounder can determine a wide profile of depths.
The multibeam
echo sounder is an improvement on the conventional echo sounder.
Instead of calculating a single depth value for the spot beneath the ship,
a multibeam echo sounder can determine a wide profile of depths in a line
perpendicular to the ship's direction of travel. (See top diagram on the
right.) When the results of many depth soundings from a moving ship are
collected, as illustrated in the lower diagram, the result is a "swath"
of depth values along the ship track.
A multibeam echo sounder uses two series of transducers
that send or receive "beams" of sound. The transmitting transducer
emits an upside-down, fan-shaped pulse of sound. The sound bounces off the
seafloor, then returns to the receiving transducer, which calculates the
distance to the seafloor from each point along the outer edge of the "fan."
Typically, a multibeam sonar calculates about 60 depth
values in each cross-track profile and the bathymetry data swath is 2-3
times the water depth. By collecting a grid of such swaths, a detailed 3D
map of the sea bottom can be constructed.
Take a closer look [50 K] at how the multibeam echo sounder works.
http://oceanography.tamu.edu/Quarterdeck/1998/3/sager-4.html
Copyright 1998-1999, Department
of Oceanography, Texas A&M University.
Updated November 24, 1998. (abdw)
Send Quarterdeck inquiries to quarterdeck@ocean.tamu.edu.
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