JRC JMA-993-SA Instruction Manual page 215

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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
F i g . 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.
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