Garmin GPSMAP 292 Owner's Manual page 89

Whiteline
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. These images show the Classic
Black color scheme.
Thick
Whiteline: Hard
bottom
Whiteline On
GPSMAP 292/298 Owner's Manual
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 See-Thru
technology, which allows the GPSMAP 292/298 to hear both weak
and strong signals simultaneously so as to identify fish returns
under the toughest conditions, such as suspended in thermoclines
or even hiding near structures. See-Thru technology allows the
transducer to see through thermoclines and locate fish. This image
is in the Classic Black color scheme
Whiteline Off
U S > U
SING ONAR NDERSTANDING
®
Thermocline
S
ONAR
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