Operations Manual

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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.
Structure ID®: Structure ID® is a Humminbird® feature that describes the traditional
grayscale method of presenting sonar information. See Grayscale.
Surface Clutter: Surface Clutter is a phenomenon where sonar returns are reflected
off of tiny objects near the surface of the water, including algae and even air
bubbles. Typically, saltwater environments have significantly greater surface clutter
than freshwater due to continuous wind and wave action that causes aeration at the
surface. The Surface Clutter menu provides manual 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 very close to structure).
Humminbird® findfinders provide a very good 2 1/2 inches of target separation in
shallower than 100 feet of depth. Target separation decreases as depth increases
due to the need for a longer Pulse Width to achieve greater depth. See Pulse Width.
Thermoclines: Thermoclines are water layer(s) of distinctly different temperatures
that create a sonar reflection due to the density of the differing 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 above or 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.
Total Screen Update®: A Humminbird® feature that refreshes and updates all the
sonar information on the display when a range change occurs. Without Total
Screen Update®, only the most recent sonar information would be drawn to the
new range, and the old sonar information would continue to scroll off the screen
at the old range.