Sea Surface Reflections; Wake - Furuno CSH-7 Operator's Manual

Sea Surface Reflections

Wake

Own
ship
To reduce sea surface reflections, set the tilt angle to 5 or higher,
so the upper edge of the sonar beam does not hit the sea surface,
or adjust TVG. When a narrow tilt angle is used, sea surface
reflections cover a large area as illustrated below.
Sea surface
Tx 16
Rx 19
Sea surface
Tx 16
Rx 19
Figure 6-3 Sea surface reflections
A wake produced by own ship or another ship can be a strong
reflecting object when a narrow tilt angle is used. As the wake
appears as a thick continuous line, it can be easily distinguished
from a fish school. A wake contains many air bubbles which
attenuate ultrasonic energy, making it difficult to sound beyond
the wake.
Other
ship
Own ship's
screw noise
Wake produced
by other ship
Figure 6-4 Wake appearance on the display
Own ship's wake
Own ship's
(produced when
screw noise
own ship turned)
Tilt angle
indication
Sea surface
reflections
6-3