2-6
However if the sea is not calm enough, they will become domi-
nant and interfere with observation of wanted echoes. To mini-
mize these sea surface reflections and to search surface fish
schools effectively, the tilt angle is usually set between 5
°
and
6
°
so the upper portion of the beam becomes almost parallel
with the sea surface. When the sea is rough, it is often set to a
little larger angle.
Tilt angle 0
°
Sea surface
Tilt angle 5-7
°
Sea surface
11
°
11
°
R400
T 15
Tilt
angle
Figure 2-5 Tilt angle and sea surface reflections
Suitable tilt angle
The figure below illustrates the relationship among tilt angle,
depth and detection range. Refer to it to find out the suitable tilt
angle for a given depth/detection range.
100
(200)
200
(400)
300
(600)
400
(800)
Range (m)
0
°
5
°
10
°
15
°
20(40)
40(80)
60(120)
80(160)
100(200)
200(400)
Vertical width of sonar beam
13
°
23 m
100 m
100 m
300 m
68 m
200 m
Depth (m)
46 m
Tilt angle and beam coverage (frequency, 60 kHz, vertical beamwidth, 13
°
Figure 2-6 Tilt angle and beam coverage
