Thermoclines Water layer(s) of disti nctly di fferent temperatures that c reate a sonar reflection due tothe densityof the differing water temperatures. Typically a thermocline will appear as a continuous band crossa thedisplay at somedistanceabove the bottom contour. Thermoclines are of interest to angler s b ecause fish will su spend ab ove or b elow the thermocline as theyseek 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 con verts the electrical energy from the transmitter into sound energy, andthat forms the sonar beam in turn. Internaly, the transducer consists of one or more piezo electric disks that expand by very minute amounts to create the sound wave. This elementalso works in reverse, converting the returned soundenergy back into an electrical signal that the receiver interprets. See SONAR.

Zoom A f eature t hat foc uses on a smaller are a of the b ottom to p rovide enhanced resolution. With enha nced resolution, the ang ler can mo re easi ly 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 zo om, 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 preferred bymany saltwater anglers.

Glossary

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