JRC JMA-5212-4, User Manual

Page: 323 / 494

6.3 SEA CLUTTER AND RAIN AND SNOW CLUTTER
66
6
yyy
yyy
6.3
SEA CLUTTER AND RAIN AND SNOW
CLUTTER
In addition to the echo required for observing ships and land radar video image also includes unnecessary echo,
such as reflection from waves on the sea surface and reflection from rain and snow. Reflection from the sea
surface is called "sea clutter," and reflection from rain and snow is called "rain and snow clutter," and those
spurious waves must be eliminated by the clutter rejection function.
[I] Sea clutter
Sea clutter appears as an image radiating outwardly from the center of the radar display and changing
depending on the size and the shape of waves. Generally, as waves become larger, image level of the sea
clutter is intensified and the clutter far away is also displayed. When waves are large and the sea clutter
level is high, it is difficult to distinguish sea clutter from a small boat whose reflection intensity is weak.
Accordingly, it is necessary to properly adjust the sea clutter rejection function. Table 6.2 shows the
relation between the sea state (SS) showing the size of waves generated by wind and the radar's detection
probability.
Table 6.2 Sea state and probability of target detection
S band radar (probability to detect a target at a distance of 0.4 NM)
X band radar (probability to detect a target at a distance of 0.7 NM)
V: Detection probability of 80 %
M: Detection probability of 50 %
NV: Detection probability of less than 50 %
RCS SS1 to 2 SS2 to 3 SS3 to 4 SS4 to 5
0.1m
2
V V-M M-NV
0.5 m
2
V V V-M M-NV
1 m
2
V V V V-M
RCS SS1 to 2 SS2 to 3 SS3 to 4 SS4 to 5
1m
2
V-M M-NV
5 m
2
V V-M M-NV
10 m
2
V V V V-M