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Glossary
Sonar Terms:
Alarm, Depth: Depth Alarm is a user-controllable, audible alert that sounds when depth is less
than or equal to the setting.
Alarm, Temperature: Temperature Alarm is a user-controllable, audible alert that sounds when
the water surface temperature equals the setting.
Backlight: Backlight is a user-controllable illumination for the LCD for night and low light use.
Beam (Sonar Beam): A sonar beam is the wide, cone-shaped projection of sound waves formed
as sound travels underwater. See Cone Angle.
Big Digits View: Big Digits View is a Humminbird® feature that displays the sonar graph and
enlarged digital readouts for easy reading from a distance. This is a great tool when monitoring
the digital depth is important - such as with higher boat speeds, or when viewing the unit from
a distance. When speed input is available, the Big Digits View also shows the TripLog. See TripLog.
Bottom Black: Bottom Black is a Humminbird® feature that "fills in" the area of the display below
the bottom contour. Bottom Black is preferred by some anglers because of its high contrast and
easy readability, even though it can obscure bottom hardness information.
Bottom Contour: Bottom Contour is the profile of the bottom graphed to the display as the
depth changes.
Bottom Hardness: Bottom Hardness is the density (or composition) of the bottom, which can
often be determined by interpreting the main sonar return. Varying levels of hardness can be
determined by interpreting the "thickness" of the sonar return. Hard returns appear thin and
black, softer returns appear thicker and less black. It is important to note that a sonar return from
a sloping bottom can have the appearance of a softer bottom.
Cavitation: Cavitation is the effect of air bubbles created as the propeller rotates and the boat
moves through the water.
Chart Speed: Chart Speed is a user-controllable feature that sets the speed at which sonar
information moves across the display. A faster setting displays sonar information from more
pings and shows more detail, but the information moves quickly across the display: a slower
setting permits viewing of more sonar history, but does not display as much detail. The best
setting is often the user's personal choice.
Cone Angle: The cone angle is the angular measurement of the sonar beam at a specific dB down
point (i.e. -10 dB). See dB Down Point.