Furuno CH-300 - Manual (Page 33)

2. HORIZONTAL MODE
2-7
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, 2 and 3 are relative to the bottom pictured above.)
Case 1 Case 2
Case 3
Detecting beam and fish position
Using the above three cases, fish schools will be displayed as below.
Case 1
Bottom
Case 2 Case 3
Bottom
Fish school "b"
Fish school "b"
Fish school "b"
Bottom
Fish school "a"
Fish school "a"
Fish school "a"
Bottom
Fish echo and tilt angle
Case 1(Tilt angle 30
° to 40 °):
Fish school “a” and “b” are just above the bottom echo.
Case 2(Tilt angle 10
° to 20 °):
Fish school “b” is clearly seen. Fish school “a” is behind
the bottom echo therefore it is difficult to discern.
Case 3(Tilt angle 0
° to 5 °):
Bottom echo is weak so fish school “b” is easily seen.
Fish school “a” is masked by the bottom echo so it is
difficult to discern. However, larger fish schools may
appear in this condition.