Bottom Echo And Tilt Angle; How To Discriminate Fish Echoes From The Bottom - Furuno CH-250 Operator's Manual

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
Case 2(Tilt angle 10 to 20
Case 3(Tilt angle 0 to 5
Case 1
Fish school "a"
Bottom
Fish school "b"
2-6
Fish school is obscured by the bottom.
Fish school is located above the bottom (midwater).
Fish school is located close to the bottom.
Case 2
Fish school "a"
Bottom
Fish school "b"
Case 1
Figure 2-7 Fish echo and tilt angle
Case 3
Fish school "a"
Bottom
Fish school "b"
Case 2
Case 3