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Setting Up Sonar
Use the Sonar tab on the Main Menu to set up the Sonar Page.
Main Menu—Sonar Tab
Fish Symbols—select how the Sonar Page shows underwater targets
and background information. Select Off to show all of the available
information about the underwater environment. Select a sh symbol,
to show only the information related to that symbol.
Water Type—select the proper water type you are boating in.
Because sound waves travel through fresh and salt water at different
rates, it is necessary to select the water type to ensure accurate
readings on the unit.
Depth Number—select how efcient the digital depth update rate
is. Fast Update updates quicker and is recommended for low-noise
water deeper than 50 feet. Auto is best for shallow water or high-
noise areas, has a slower screen update, and is best used if you travel
a wide variety of depths.
If the unit is unable to track the bottom for any reason, the digits in
the depth window ash on and off to alert you that the unit is not
tracking the bottom.
Map Split Sonar Detail—select how much detail appears on the
Map Page with the sonar shown. Full Range shows data using the
Range setting of the Sonar Page, regardless of Zoom or Bottom
Lock. Maximum Detail shows any Zoom or Bottom Lock data
from the Sonar Page.
Keel Offset—enter the surface reading for the depth of a keel. This
makes it possible to measure depth from the bottom of your keel
instead of from the transducer’s location. Enter a positive number
to offset for a keel. It is also possible to enter a negative number to
compensate for a large vessel that can draw several feet of water.
The Keel Offset is reected in the depth reading.
Transducer—select the type of transducer that you are using. If you
are using a speed-capable transducer/sensor, select Temp, Spd.
GPSMAP 278 Owner’s Manual 95
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