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Glossary Sonar Terms
Pixels: Pixels are the "picture elements", or small square blocks, that make up the image on the LCD. Measured as a
vertical by horizontal number (i.e. 640 V x 320 H), this key specification typically indicates the quality of resolution. In
fishfinders, the total resolution (vertical multiplied by horizontal) is often less important than the "Vertical Pixel"
resolution. See Pixels, Vertical.
Pixels, Vertical: Vertical Pixels are a number of vertical picture elements in a single column on an LCD display. A greater
number of vertical pixels provide finer resolution of targets detected by sonar. Essentially, a vertical distance (the depth),
when divided by a larger number, breaks that distance into smaller samples, each representing a smaller area and thus
providing more detail. In fishfinders, vertical pixels are more critical than horizontal pixels because the horizontal axis of
the display represents time, or history. Sonar information on the horizontal axis can vary greatly, depending on boat
speed and the Chart Speed setting. A greater number of horizontal pixels show more sonar history that the boat has
passed through. On many models, Humminbird® provides the most vertical pixels to provide a better display resolution.
See Chart Speed and Pixels.
Power Output: Power output is the amount of sound energy emitted into the water by the sonar transmitter. Power
output is measured using either RMS (Root Mean Square) or P-T-P (Peak-to-Peak) measurement systems. Either method
is acceptable, but it is important, when comparing power outputs, to make sure that the same measurement system is
being used for both outputs, because P-T-P numbers are 8 times higher than RMS numbers. Greater power output allows
the sonar signal to penetrate through weeds and thermoclines, reach deeper depths and operate more effectively in
noisy environments, such as when the boat is running at high speed.
Pulse Width (Pulse Length): Pulse Width is the length of time that a sonar sound burst is transmitted into the water.
Shorter pulse widths provide better target separation, but cannot travel to great depths. Longer pulse widths provide
better depth penetration, but result in poorer target separation. Humminbird® varies pulse width based on depth to
optimize both target separation and depth performance. See Target Separation.
QuadraBeam PLUS™: QuadraBeam PLUS™ is a Humminbird® sonar configuration that uses four sonar beams for a
more detailed bottom image. QuadraBeam PLUS™ uses the DualBeam PLUS™ configuration for downlooking, and also
adds two additional beams to look to the left and right. The sonar beams pointing to the left and right provide the ability
to spot fish and structure over a wide 90° area, and to identify on which side of the boat they are located. See
DualBeam PLUS™.
Quick Disconnect Mount: The Quick Disconnect Mounting system is an exclusive Humminbird® feature that permits
the unit to be easily removed from the mounting base by pressing a release button, and re-installed by simply snapping
it back into place. All cable connections are made when installing, so that no separate wiring connections are required.
Additionally, the mount offers 90° tilt and 360° swivel capability to adjust the viewing angle of the unit as you move
about the boat.
Real Time Sonar: Real Time Sonar is a Humminbird® technology that delivers ultra-fast sonar transmitter/receiver
operation and results in a more detailed instantaneous view of what is under the boat. The Real Time Sonar window is
a vertical band at the right side of the display that shows the instantaneous sonar return from the transducer at a
particular instant. The RTS® Window menu option permits the user to adjust the window to show the full sonar signal
return, or just a narrower band that indicates intensity using grayscale. Real Time Sonar relies on very fast Sonar Update
Rate (Ping Speed). See Sonar Update Rate.
Receiver: See Transmitter.
Second Return: The Second Return is a term that describes the appearance of a second sonar return below the primary
sonar return (bottom contour) at exactly twice the true depth. The second return is caused by the same sonar energy
bouncing off the bottom once, rebounding to the water surface and then traveling back down to the bottom to be
reflected again. Second returns are more common in shallow water and over hard bottoms; it is actually possible to see
a third sonar return under some circumstances. The second return provides useful information to help determine bottom
hardness, as areas with harder bottoms will generally create a second return. The second return can be used as a guide
to set Sensitivity when in shallower water.
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.
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