Furuno CSH-5 MARK-2 - Manual (Page 18)

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Seabed Echo vs Tilt Angle
Case 1: Tilt Angle 30 to 40 degrees
A wide tilt angle will display the entire seabed since it is captured by
the full width of the beam.
Case 2: Tilt Angle 10 to 20 degrees
A narrow tilt angle will display only half the seabed since it is cap-
tured by only the lower half of the beam.
Case 3: Tilt Angle 0 to 10 degrees
An exceptionally narrow tilt angle may or may not capture the sea-
bed since the returning echo is weak.
Example of How to Discriminate Fish Echoes
from the Seabed
The following figure illustrates how two fish schools a and b are
displayed on screen using three different tilt angles.
Case 1: Tilt angle 30 to 40 degrees
Fish school is obscured by the seabed.
Case 2: Tilt angle 10 to 20 degrees
Fish school is located above the seabed (midwater).
Case 3: Tilt angle 0 to 10 degrees
Fish school is located close to the seabed.
Case 1 Case 2 Case 3
a a a
b
Fish School a Fish School a Fish School a
Seabed
Seabed
Seabed
Case 1 Case 2 Case 3
b