6
moving up and down over flat bottom, the bottom depiction often appears
in regular variations that match wave timing.
Structure.
Structure is defined as any object physically attached to the bot-
tom. The sonar configuration of the Pro Craft unit is optimized to give the
most accurate depiction of bottom structure possible. Grass, trees, stumps,
wrecks or other debris are accurately displayed, however the depiction of
these objects varies with boat speed and direction. The best way to learn to
interpret structure is to operate the Pro Craft unit over a variety of known
conditions and experiment with user functions to best represent those con-
ditions on-screen.
Surface Clutter.
Surface clutter is the layer of water near the surface that
is rich in algae and other growth, and often is aerated by wind or wave
action. This area of water interferes with sonar transmission and often
appears on-screen as regular clusters of individual dots near the “0” line.
Thermoclines.
Thermoclines are sharp
differences in water temperature.
These are easily identified by the con-
tinuous nature of the return.
Second Returns.
When a sonar signal
is reflected off the bottom back to the
transducer, there is often enough ener-
gy left in the signal to be reflected off
the surface of the water back to the
bottom a second time. Second returns
appear as a slightly weaker bottom
representation exactly twice the depth
of the primary bottom return. The sec-
ond return is most likely to occur in
shallow water and in areas of relatively
hard bottom.
Fish ID.
The Pro Craft unit uses advanced signal processing to further eval-
uate any sonar return between the surface and the bottom. For instance, a
small school of bait fish usually appears as a dense cluster of individual dots.
If the return meets certain additional criteria, a fish symbol will be assigned.
USING THE PRO CRAFT UNIT
WHAT YOU SEE ON SCREEN
Thermocline Second Return
