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SETTING UP AND USING SONAR > UNDERSTANDING SONAR
Whiteline
The GSD 20 Sounder Module can help you determine whether the bottom is hard or soft. When the sonar sound waves 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, a red line is used 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 the bottom layer information easier to distinguish.
Thick
Whiteline: Hard
bottom
Whiteline On | Whiteline Off |
Thermoclines
A rough definition of a thermocline is a break in water where the water temperature changes faster than the water above it. Thermoclines are shown as the weakest colors.
One of the unique features offered by Garmin is
Thermocline
130 | GPSMAP 296 Pilot’s Guide |