Furuno CSH-5L/CSH-8L manual Sea Surface Reflections, Wake, Sea surface reflections

6. INTERPRETING THE DISPLAY

6.3Sea Surface Reflections

To reduce sea surface reflections, set the tilt angle to 5° or more so that the upper edge of the sonar beam does not hit sea surface, or adjust the TVG functions. When the sonar is used with a narrow tilt angle, the sea surface reflections cover a large area (up to 300 m to 400 m) as illustrated below.

	Sea surface	Tilt angle
		indication
Tilt: 0˚
		Sea surface
	Sea surface	reflections
Tilt: 5-6˚

Sea surface reflections

6.4Wake

A wake produced by own ship or another ship can be a strong reflecting object when the sonar is used with a narrow tilt angle. As the wake appears on the screen as a thick continuous line, it can be easily distinguished from a fish school. On the other hand, the wake contains a lot of air bubbles which attenuate ultrasonic energy, making it often 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 turns)

Wake

6-3