Insignia 450TX - Manual (Page 12)

Bottom. The graphic depiction of the bottom provides the user with an
effective tool for understanding the composition of the bottom. The FSTN
type display uses 4 discrete levels of gray to indicate the intensity of the
returned sonar signal. The 450TX can display even the smallest sonar
returns with light gray pixels. Larger returns are displayed with darker
shades of gray. If the bottom is hard and smooth, the bottom depiction is
narrow and dense. If the bottom is soft mud or sand, the depiction will be
thick and less dense. This indicates that much of the signal is absorbed by
the soft bottom. If the bottom is rocky or rugged in composition, the
depiction is of varying density and textured in appearance.
Wave action also affects the bottom depiction. The information drawn is a
distance measurement, so if the boat is 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
bottom. The sonar configuration of the 450TX 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 450TX 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.
10
USING THE 450TX
WHAT YOU SEE ON SCREEN
Thermocline Second Return
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