Furuno CSH-84 - Manual (Page 85)

11-3
Sea Surface Reflections
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
Sea surface
15°
Tilt angle
indication
Sea surface
reflections
15°
Figure 11-3 Sea surface reflections
Wake
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.
Own
ship
Other
ship
Wake produced
by other ship
Own ship's
screw noise
Own ship's
screw noise
Own ship's wake
(produced when
own ship turned)
Figure 11-4 Wake appearance on the display