Garmin 240 - Manual (Page 39)

31
On the Water
31
On the Water
Understanding the Chart
Whiteline
The Fishfi nder 240 can help you to determine if the bottom is hard
or soft. When the sonar soundwaves are refl ected back by the bottom, a
hard bottom will return a stronger signal than a soft bottom. The stronger
bottom return, the wider the bottom layer is displayed. The unit uses
the whiteline function to make this bottom layer information easier to
distinguish.
When viewing the display without Whiteline active, the bottom return
is black. While you can make some determination of the bottom type,
the black return makes this more diffi cult. With the whiteline active the
bottom return appears layered in shades of gray and black and makes
determining the bottom type easier and more reliable. Example 3 shows
the bottom return with and without the whiteline activated.
Whiteline Turned Off Whiteline Active
Hard
Bottom
Soft
Bottom
Whiteline
Example 3.
Whiteline can also help you to determine the type
of bottom structure that is displayed on chart. 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
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