How Sonar Works - Humminbird 747c Operation Manual

531526-1_A - 747c_&_777c2_Man_Eng.qxp

How Sonar Works

Sonar technology is based on sound waves. The 700 Series™ Fishing System
uses sonar to locate and define structure, bottom contour and composition, as
well as depth directly below the transducer.
Your 700 Series™ Fishing System sends a sound wave signal and determines
distance by measuring the time between the transmission of the sound wave
and when the sound wave is reflected off of an object; it then uses the
reflected signal to interpret location, size, and composition of an object.
Sonar is very fast. A sound wave can travel from the surface to a depth of
240 ft (70 m) and back again in less than 1/4 of a second. It is unlikely that
your boat can "outrun" this sonar signal.
10/2/2006
SONAR is an acronym for SOund and NAvigation
Ranging. Sonar utilizes precision sound pulses or
"pings" which are emitted into the water in a
teardrop-shaped beam.
The sound pulses "echo" back from objects in the
water such as the bottom, fish and other
submerged objects. The returned echoes are
displayed on the LCD screen. Each time a new
echo is received, the old echoes are moved
across the LCD, creating a scrolling effect.
When all the echoes are viewed side by side, an
easy to interpret "graph" of the bottom, fish and
structure appears.
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