Furuno GP-3700F, Operator'S Manual

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11. ECHO SOUNDER
11-5
11.2.6 Bottom discrimination display (50 kHz or 200 kHz)
The bottom discrimination (seabed composition) display shows the normal display as
the right half, the left half of the display is split in half horizontally with the bottom zoom
display on the upper half and the bottom discrimination display on the lower half. A
bottom displayed with a short echo tail usually means it is a soft, sandy bottom. A long
echo tail means a hard bottom.
11.2.7 A-scope display (50 kHz, 200 kHz or dual frequency)
The A-scope display shows echoes at each transmission with amplitudes and tones
proportional to their intensities, on the right of the screen. It is useful for estimating fish
species and seabed composition.
Bottom lock display
Single frequency display
Bottom discrimination display
Bottom trail
Long: Hard bottom
Short: Soft bottom
Single frequency display
A-scope display
Weak echo
(small school of fish
or noise)
School of fish
Strong echo
(bottom)
When [A-SCOPE PEAK HOLD] is
set to [SHOW], peak-hold amplitude
picture is displayed in dots.