Raymarine C Series Reference Manual page 158

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How is a risk assessed?
Each target is monitored to see if it will be within a certain distance from your boat
within a certain time. If so, the target is designated as dangerous and an audible
warning is sounded along with an on-screen warning being shown. The target symbol
changes to the dangerous target symbol and flashes to indicate that it is a dangerous
target. Pressing the appropriate soft key will silence the alarm and remove the
warning.
If a target is lost, either because the MARPA software has lost contact with it, or
because it has moved out of range, an audible alarm is sounded and an on-screen
warning appears. The on-screen symbol will change to the target lost symbol. Pressing
the appropriate soft key will silence the alarm and remove the on-screen warning and
the target lost symbol.
How far from my boat does MARPA work?
MARPA target acquisition is only available at radar range scales of up to 12nm,
although tracking continues at all ranges.
If you change to a smaller range scale, targets may be beyond the range of your
scanner and will be lost. In such cases, an on-screen warning will indicate that the
target is off-screen.
What happens to target data?
All MARPA targets are stored in a MARPA database list which shows the following
information:
TARGET
TRACKING
Target display
Each target is displayed as a symbol which indicates its status:
MARPA LIST...
Target being acquired
Safe target
C-Series Display Reference Manual
MARPA LIST
True
True
ID Bearing Range
Course Speed
o
o
022 T
1 0.000nm 180 T 0.0kts
o
o
025 T 0.000nm
2 180 T 0.0kts
Dangerous target
Lost target
CPA TCPA
0.000nm 00h00m00s
0.000nm
00h00m00s