Furuno CSH-53 manual Sea Surface Reflections, Wake, 3 Sea surface reflections

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	Tilt angle
	indication
15°
	Sea surface
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.

Other ship

Own ship

Own ship's screw noise

Wake produced
by other ship	Own ship's wake
Own ship's
	(produced when
screw noise	own ship turned)

Figure 11-4 Wake appearance on the display

11-3