Raytheon HSB L755, Owner'S Handbook Manual

Page: 117 / 224

Chapter 4: Fishfinder Operations 4-3
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In Bottom lock mode the fish arches may appear distorted as the bottom
topography is removed from the image.
Bottom Indications
The bottom usually produces a strong echo, so it is easy for the Fishfinder to
see a lot of detail. The Fishfinder can indicate many different kinds of bottom
conditions.
As illustrated in Figure 4-2, a hard bottom appears as a thin line.
Figure 4-2: Fishfinder Bottom Indications
An uneven bottom which is covered with rocks or coral produces a complex
display; the bottom image is irregular, with long tails pointing upward. A
wreck produces a similar image.
A softer bottom or a bottom covered with seaweed produces a wide line, as the
sound waves reflect from different layers of the bottom. In Figure 4.2b, the
Fishfinder is getting a good echo from the bottom, so the upper layer of the
bottom is shown as dark gray. Notice that the lower layer of the bottom is
shown as a lighter gray, this indicates a weaker echo. This could mean that the
upper layer is soft; some sound waves may get through this layer and be
reflected as a more solid layer below.
D5016-1
A
Hard bottom (sand)
B
Soft bottom (mud)
C
Rocky bottom
D White line feature on: