Furuno GP-3500F - Manual (Page 216)

11. VIDEO SOUNDER OPERATION
11-44
Current rip
A current rip develops when two ocean currents of different speeds, directions
and water temperatures meet. Its on-screen appearance is as shown below.
Current Rip
Current rip
Surface noise
When the sea is rough or the ship passes over a wake, surface noise may
appear at the top of the screen. It can be suppressed with the CLUTTER
FUNCTION.
Surface Noise
Surface noise
Aerated water
When the sea is rough or the ship makes a quick turn, gaps in the bottom echo
on the screen may appear. This is caused by air bubbles which block
propagation of the sound wave. Generally low frequency ultrasonic waves are
interrupted more easily than high ones.
Ultrasonic wave
blocked by
aerated water
Aerated water