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2-4
2.2.3 Virtual image
A relatively large target close to your ship may be represented at two positions on the
screen. One of them is the true echo directly reflected by the target and the other is a
false echo which is caused by the mirror effect of a large object on or close to your ship
as shown in the figure below. If your ship comes close to a large metal bridge, for ex-
ample, such a false echo may temporarily be seen on the screen.
True
echo
False
echo
Own
ship
Target ship
Mirror image
of target ship
Figure 2-4 Virtual image
2.2.4 Shadow sectors
Funnels, stacks, masts, or derricks in the path of the antenna block the radar beam. If the
angle subtended at the antenna is more than a few degrees, a non-detecting sector may
be produced. Within this sector targets can not be detected.
Radar
antenna
Radar
mast
Shadow sector
Figure 2-5 Shadow sectors