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Sensitivity:
Sensitivity is a user feature that adjusts the sensitivity of the sonar
system to show more or less detail in the water. Higher sensitivities are often
preferred, however, when the water contains debris (silt, storm debris, etc.) and it
can be difficult to pick out targets. Conversely, if sensitivity is set too low, relevant
targets may be missed.
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.
Glossary
47866_798c-ci_Man_531691-1_F:531519_Eng 10/23/09 2:26 PM Page 186
