On the Water
Whiteline and Thermoclines
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Whiteline 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— | Structure is soft— |
probably a rock or stump | probably a mud pile |
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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 the whiteline
function to make this bottom layer information easier to distinguish.
With the Fishfinder 250/250C, whiteline helps accentuate where strong signals are located, which make bottom type determination easier. The example to the right shows the bottom return with and
without the whiteline activated. | Whiteline | Soft Bottom | Hard Bottom | Whiteline Turned Off |
See page 14 for more information. |
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Thermoclines
One of the unique features offered by Garmin is
clines. A rough definition of a thermocline is a break in
water where the water temperature changes faster than in Thermocline the water above it. Thermoclines give weak returns and are
shown as the weakest colors/shades (see pg. 11).