Furuno NAVNET 1823C - Manual (Page 152)

4. VIDEO SOUNDER OPERATION
4-6
Bottom-lock display
The bottom-lock display provides a compressed normal picture on the right half
of the screen and a 10 or 20 feet (3 or 6 meter) wide layer in contact with the
bottom is expanded onto 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 from the SOUNDER RANGE SETUP menu. For details, see paragraph
5.9.3.
HF
80
This part
is zoomed.
Fish
school
Zoom marker
NORMAL DISPLAY BOTTOM-LOCK
DISPLAY
50
0
100
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-
-
-
-
-
-
-
-
-
10
8
6
4
2
0
10
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Bottom-lock display plus normal sounder display