Furuno GP-3700F, Operator'S Manual

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11. ECHO SOUNDER
11-4
11.2.4 Bottom zoom display (50 kHz or 200 kHz)
The bottom-zoom display expands bottom and bottom fish echoes by the zoom range
selected on the menu (see section 11.20). This mode is useful for determining bottom
contour. When the bottom depth increases, the display automatically shifts to keep the
bottom echo at the lower part of the screen.
11.2.5 Bottom lock display (50 kHz or 200 kHz)
The bottom-lock display provides a normal picture on the right half of the screen and
a 2 to 10 meters (7 to 30 feet) wide layer in contact with the bottom is expanded on
the left half of the screen. This mode is useful for discriminating bottom fish from the
bottom echo. You may select the bottom lock range. Refer to section 11.20.
Single frequency display
Zoom marker
(switched with depth)
Bottom zoom display
Single frequency display
Zoom marker
This area is zoomed.
School of fish
Zoomed school of fish
Bottom displayed flat
Bottom lock display