Furuno CH-250 manual Bottom echo and tilt angle, How to discriminate fish echoes from the bottom

2.6.1 Bottom echo and tilt angle

Refer to the illustration below.

Case1: Tilt angle 30° to 40°

This tilt angle will display the entire bottom since it is captured by the full width of the beam.

Case2: Tilt angle 10° to 20°

This tilt angle will only display half the bottom since it is only captured by the lower half of the beam.

Case3: Tilt angle 0° to 5°

This tilt angle may or may not capture the bottom since the returning echo is weak.

2.6.2 How to discriminate fish echoes from the bottom

The figure at the bottom of the page illustrates how two fish schools “a” and “b” are displayed on the screen using three different tilt angles.

Case 1(Tilt angle 30° to 40°): Fish school is obscured by the bottom.

Case 2(Tilt angle 10° to 20°): Fish school is located above the bottom (midwater).

Case 3(Tilt angle 0° to 5°): Fish school is located close to the bottom.

Case 1 Case 2 Case 3

Fish school "a" Fish school "a" Fish school "a"

Bottom		Bottom		Bottom
		Fish school "b"		Fish school "b"
Fish school "b"
	Case 1		Case 2		Case 3

Figure 2-7 Fish echo and tilt angle

2-6