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7.2
Intensity Reflected from the Target
The signal intensity reflected from a target depends not only on the height and size of the target but
also on its material and shape. The echo intensity from a higher and larger target is not always higher
in general. In particular, the echo from a coast line is affected by the geographic conditions of the coast.
If the coast has a very gentle slope, the echo from a mountain of the inland like the figure below
appears on the radar display. Therefore, the distance to the coast line should be measured carefully.
The next table shows the relation between the target detection range and the radar reflection
cross-sectional area (RCS) with regard to the type and the height of the target in a situation in which
the weather is good, the sea state is calm and the radio wave propagation is normal. As revealed by
this table, even on the same sea shore line, detection range greatly differs depending on the height of
the target from the surface of the sea. Furthermore, because the target detection range is greatly
influenced by the shape and material of the target and environmental conditions, such as the sea state,
weather, and radio wave propagation, caution should be taken when detecting range of target.
Relation between Type and Height of Target and Detection Range and RCS
Type of target
Sea shore line
Sea shore line
Sea shore line
SOLAS target ship (>5000GT)
SOLAS target ship (>500GT)
Small boat with IMO standard
compatible radar reflector
Marine buoy with corner reflector
Standard marine buoy
10-metre small boat without radar
reflector
Waterway location beacon
Memo
Detection range shown in the above table may greatly decrease depending on the shape of the
target, sea state, weather and radio wave propagation conditions.
Mountain displayed
on the radar display
Sea shore line not displayed
on the radar display.
Sea Shore Line Not Displayed on the Radar Display
Height from
sea surface
(m)
60
6
3
10
5
4
3.5
3.5
2
1
Detection range (NM)
X band
S band
20
20
8
8
6
6
11
11
8
8
5.0
3.7
4.9
3.6
4.6
3.0
3.4
3.0
2.0
1.0
7-3
Section 7 True and False Echoes on Display
HL
RCS (m²)
X band
S band
50,000
50,000
5,000
5,000
2,500
2,500
50,000
30,000
1,800
1,000
7.5
0.5
10
1
5
0.5
2.5
1.4
1
0.1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
付録
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