Virtual Image; Shadow Sectors - Furuno FR-7041R-MARK-2 Operator's Manual

2. INTERPRETING THE DISPLAY
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 example, such a false echo may temporarily be seen on
the screen.
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.
2-4
Target ship
Own
ship
True
echo
Mirror image
of target ship
Figure 2-4 Virtual image
Radar
mast
Shadow sector
Figure 2-5 Shadow sectors
False
echo
Radar
antenna