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BASIC OPERATION > UNDERSTANDING SONAR
34 Fishfinder 250/250C Owner’s Manual
Whiteline
The Fishfinder 250/250C can help you to determine if the bottom is
hard or soft. When the sonar soundwaves are reflected back by the
bottom, a hard bottom returns a stronger signal than a soft bottom.
A thin whiteline indicates a softer bottom while a thick whiteline
indicates a harder bottom. Normally, the Fishfinder 250 uses a black
line and the Fishfinder 250C uses a red line to show the point where
water meets the bottom. This line follows the bottom contour, along
with any significant objects lying on the bottom. The unit uses
whiteline to make this bottom layer easier to distinguish.
With the Fishfinder 250/250C, whiteline helps accentuate where
strong signals are located, which makes bottom type determination
easier. The example to the right shows the bottom return with and
without the whiteline activated. See page 18 for more information.
Whiteline turned Off
Whiteline
Hard bottom
Soft bottom
Whitelines can also help you to determine the type of bottom
structure that is displayed on the graph. By determining the hardness
of the structure, you can make a better informed decision on the type
of structure.
Structure is hard—
probably a rock or stump
Structure is soft—
probably a mud pile