Structure: Structure is a g eneral term for objects on the bottom that present a discontinuity and are a likely attractor for fish. This includ es bottom c ontour features
Structure ID® : Structure ID® is a Humm inbird® f eature that describes the traditional grayscale method of presenting sonar information. See Grayscale.
Surface C lutter: Surface Clutter is a ph enomenon where so nar retur ns are reflected off of tiny objects nearthe surface of the water,including algae and even air bubbles. Typically, saltwater environments have significantly greater surface clutter t han f reshwater due to c ontinuous wind a nd wave action that causes aeration atthe surface. The Surface Cluttermenu providesmanual control to bias the default settings under extreme conditions.
Target Separation:Target Separation is the measurement of minimum distance that a fishfinder needs to be able to recognize two very close objects as two distinct targets (i.e. two fish hanging very close, or a fish hanging veryclose to structure). Humminbird® fishfinders provide a very good 2 1/2 inches of target separation in shallower than 100 eetf of depth. Targetseparation decreases as depth increases due to the need for longer Pulse Width to achieve greater depth. SeePulse Width.
Thermoclines: Thermoclines are water layer(s) of distinctly different temperatures that create a sona r reflec tion due to the density o f th e differ ing water temperatures. Typically a thermocline will appear as a continuous band across the display at some distance above the bottom contour. Thermoclines are of interest to anglers because fish will suspend aboveor below the thermocline as they seek the optimum temperature and oxygen levels.
Time Variable Gain: Time Variable Gain is a processing step applied to the sonar return to “normalize“ the data so that objects of equal size (i.e. fish) appear to be the same size, even if they are separated by a good distance. Time Variable Gain is a fundamental attribute of good sonar, but is often promoted as a feature.
Total Screen Update®: A Humminbird® feature that refreshesand updates all the sonar information on the display when a range c hange occurs. Without Total Screen Update®, only the most recent sonar information would be drawn to the
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