Humminbird 343c Operation Manual page 67

SONAR: SONAR is the acronym for SOund and NAvigation Ranging. Sonar
technology uses precision sound bursts transmitted underwater to determine the
distance and other attributes of objects in the water. Distance can be determined
because the speed of sound in water is constant, and the time for the signal to
return is measured. Sound also travels very quickly underwater, making sonar a
responsive, cost-effective tool. Sonar is the basic technology behind all recreational
and commercial fishfinding and depthfinding devices.
Sonar Echo Enhancement: Sonar Echo Enhancement is a Humminbird® feature that
describes the high degree of sonar sensitivity achieved through a combination of
transmitter/receiver and software algorithms. The result of Sonar Echo Enhancement
is to display virtually everything in the water that is of interest to the angler, including
bait fish, game fish, thermoclines, weed beds, subtle structure, and more.
Sonar Update Rate: Sonar Update Rate is the number of times per second that the
transmitter/receiver sends and receives sonar signals. A very fast sonar update rate
collects more information and provides a more detailed image of the bottom, fish
and structure. Many Humminbird® units operate at up to 40 times per second when
in single frequency operation. Due to the limitation of the speed of sound in water,
the update rate begins to slow as depth increases to deeper than 50 feet. In very
shallow water (less than 10 feet), however, update rates as much as 60 times per
second can be achieved.
Speed: Speed is the rate at which the boat moves through the water. Boat speed can be
measured as Speed Over Ground or Speed Through Water. Speed Over Ground is
provided by GPS, and is the measurement of the boats progress across a given distance.
Speed Through Water is provided by a speed paddlewheel, and is the measurement of
the flow past the boat, which may vary depending on current speed and direction.
Speed Through Water is most critical for anglers using downriggers, as it impacts the
running depth of the down riggers. Speed Over Ground is optimal for navigation, as
accurate destination times can be derived from this measurement. Humminbird®
products allow for input and display of both sources.
Structure: Structure is a general term for objects on the bottom that present a
discontinuity and are a likely attractor for fish. This includes bottom contour
features (drop-offs, humps, and holes), standing structure (stumps, timbers, brush
piles) and a wide range of other potential objects (sunken boats, reefs).
Humminbird® units excel at showing structure with great detail over a wider area
due to unique sonar configurations developed for the angler.
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