JRC JMA-9922-6XA - Strength of Reflection from the Targets; Sea Clutters; False Echoes

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Strength
of
Reflection
from
the
Targets
The
signal intensity reflected from
a tiarget
depends
not
only
on the height and size of
the target
but
also on itrs material and shape.
The echo intensity
from
a
higher
and larger trarget
is not
always
higher in
general.
In
particular,
the
echo
from
a
coastline
is
affected by the
geographic
conditions
of the coast.
lf the
coast has
a
very
gentle
slope,
the
echo
from
a
mountain on the inland
appears on
the radar
display.
Therefore,
the distance to the coastline
should be measured
carefully.
Mountain
displayed on the
radar display
Sea
shore
line not
displayed on the
radar display
Fig.6.2
Sea Clutters'
When the sea surface
ruffles,
bright
echo
returns
spread around
the center
of the
radar display.
The
higher the waves are, the echo
returns
are larger.
Swirling
cunents
may
appear as
a smooth line
like
a coastal
line.
False
Echoes
The
radar
observer
may be embarrassed
with some
echoes
that do not exist actually.
These
false
echoes appear by the following
caused that are well known:
tll
Shadow
When
the radar
scanner
is installed
near a funnel
or
masl, the echo of a target that exists
in the
direction
of the
funnel
or
mast
cannot
appear on the
radar display because the radar
beam is
reflected
on lhe funnel or mast.
Whether there is monitoring
the sea
clufter
returns
can
check
some
false
echoes
due to
shadows,
in which lhere may
be a
part
of weak or no returns.
Such
shadows appear always
in the same directions, which the operator should have in
mind in
radar operation.
6-3