Insignia 105SX - Manual (Page 12)

Structure. Structure is defined as any object physically attached to the
bottom. The sonar configuration of the 105SX 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 105SX over a variety
of known conditions and experiment with user functions to best
represent those conditions 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 continuous nature of the return.
Second Returns. When a sonar signal is reflected off the bottom back to
the transducer, there is often
enough energy 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 second return is most likely to
occur in shallow water and in areas
of relatively hard bottom.
Fish ID. The 105SX uses advanced
signal processing to further evaluate
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 is assigned. There are three
different size fish symbols used to indicate the intensity of the sonar
return. While signal intensity is a good indicator of relative fish size,
10
USING THE 105SX
WHAT YOU SEE ON SCREEN
Thermocline Second Return