Thermoclines Water layer(s) of distinctly different temperatures that create a sonar reflection due to the densityof the differing water temperatures. Typically a thermoclinewill appear as a continuousband across the display at some distanceabove the bottomcontour. Thermoclines are of interest to anglers because fish will suspend above or below the thermoclineas they seek the optimum temperature and oxygen levels.

Time VariableGain (TVG) 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.

Transducer The transducer is part of the sonar system, which mounts on the boat and is in contact with the water, that converts the electrical energy from the transmitter into sound energy,and that forms the sonar beam in turn. Internally, the transducerconsists of one or more piezo electric disks that expand by very minute amounts to create the sound wave. This element also works in reverse, converting the returned sound energy back into an electricalsignal that the receiver interprets. See SONAR.

Zoom A feature that focuses on a smaller area of the bottom to provide enhanced resolution. With enhanced resolution, the angler can more easily see fish hanging in structure or multiple fish hanging close together.

Zoom, Bottom Lock Bottom Lock Zoom is a feature that focuses on a smaller area just above the bottom to provide enhanced resolution. Unlike regular zoom, it continuously graphs the bottom at a constant point on the display regardless of changes in depth. This “flattens“ out the bottom contour, but is effective at showing fish on or near the bottom, and is preferredby many saltwater anglers.

Glossary - Sonar Terms

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