491 Echo Sounder Operations Manual
Page 71
G
Glossary
A-scope
A horizontally magnified view of each echo, where the
strength is shown by the width as well as the color of the line.
COG
C
ourse-
O
ver-
G
round. The actual path of your vessel relative
to the surface of the earth.
clutter
Distracting echoes caused by turbulence, plankton, etc. Can be
reduced by the clutter control.
current
The horizontal movement of water caused by tidal or other
forces.
default
A choice made automatically by the echo sounder; some
defaults can be overridden in partial automatic mode.
echo
The sound returned by either an object below the water’s sur-
face or by the seabed, when this object or seabed is detected
by a sound wave.
echo sounder
An instrument that uses sound waves to measure the depth of
a body of water or an object (such as a school of fish) below
the water’s surface.
fathom
A depth measurement that equals six feet or 1.83 meters of
water.
gain
The amount of amplification given to the received echo before
it is displayed.
GPS
G
lobal
P
ositioning
S
ystem.
hue
The gradations of a color.
interference
The electromagnetic interruption of a radio signal that causes
a poor signal reception. Interference may originate from exter-
nal sources, such as another nearby echo sounder, or from the
vessel itself, such as alternator noise.
latitude
Imaginary lines on the earth's surface running East/West and
expressed in degrees (0-90) north or south of the Equator.
Used in conjunction with the North/South lines of longitude to
determine position.
