Furuno GP-3700F, Руководство оператора

Страница: 181 / 224

11. ECHO SOUNDER
11-33
Bottom fish
The echoes from the bottom are stronger than the bottom fish
echoes so that you can distinguish between them by colors. The
bottom echoes are normally shown in reddish-brown or red, the
bottom fish echoes in weaker color.
Plankton, current rip
Plankton
A plankton layer appears as a large amount of green or
blue dots, and is a possible location for fish. A plankton
layer moves down in the day and up at night.
Current rip
When two ocean currents of different speeds directions and wa-
ter temperatures meet, a current rip occurs. A current rip ap-
pears on the screen as shown in the right illustration.
Surface noise
When the sea is rough or the ship moves over a wake, surface
noise can appear at the top of the screen. It can be suppressed
with the clutter function (see section 11.8).
Air bubbles in the water
When the sea is rough or the ship makes a quick turn, there can
be blank spots in the bottom echo (see the right illustration).
These blank spots are caused by air bubbles which stop the
movement of the sound wave. These air bubbles can occur with
the low frequency ultrasonic waves.
Bottom fish echo
Plankton
School of fish
Current rip
Surface noise
Ultrasonic wave
blocked by air
bubbles