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 t he acronym for S Ound an d NA vigation R anging. 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, c ost-effective too l. Sonar i s the basic technology behind al l recreational and commercial fishfinding and depthfinding devices.

Sonar Echo Enhancement:Sonar Echo Enhancementis a Humminbird®featurethat describes the high degree of sonar sensitivity achieved through a combination of transmitter/receiverand softwarealgorithms. The result of Sonar Echo Enhancement is to display virtuallyeverything inthe water that isof 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 sendsand receives sonar signals. A very fast sonar update rate collects more information and providesa more detailedimage of the bottom, fish and structure. Many Humminbird® units operate at upto 40 times persecond when in single frequency operation. Dueto the limitationof the speed of sound in water, the update rate begins to slow as depth increases todeeper 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 theboat moves through the water. Boat speed can be measured as Speed Ove r 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 depe nding on current speed and direction. Spe ed Through Water is most crit ical for ang lers using downriggers, as it impacts the running depth of the down riggers. Speed Over Gr ound i s optimal for navigation, as accurat e desti nation times can be derived f rom this measurement. Humminbird® product s all ow for input and display of both sources.

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Glossary