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2. RADAR OPERATION
2-26
2.26 ARP, TTM Operation
When the radar source is an ARP-equipped Model 18x4-BB/19x4-BB series network radar,
you can manually and automatically acquire and track ten targets. Once a target is acquired
automatically or manually it is automatically tracked within 0.1 to 32 nm. If the FURUNO
heading sensor PG-1000 is used, the data sentence “RMC” is necessary.
Alternatively, you can display the tracks of other ships by receiving the data sentence TTM
(Tracked Target Message) via the NETWORK or NMEA port on the processor unit.
However, targets cannot be acquired.
Note: When using your unit as remote display, you cannot change the range of the main
radar at the remote display. For the target acquisition, set the range individually.
Usage precautions for ARP
No one navigational aid should be relied
upon for the safety of vessel and crew.
The navigator has the responsibility to
check all aids available to confirm
position. Electronic aids are not
a substitute for basic navigational
principles and common sense.
• This auto plotter automatically tracks an
automatically or manually acquired radar
target and calculates its course and
speed, indicating them by a vector. Since
the data generated by the auto plotter
are based on what radar targets are
selected, the radar must always be
optimally tuned for use with the auto
plotter, to ensure required targets will not
be lost or unwanted targets such as sea
returns and noise will not be acquired
and tracked.
• A target does not always mean a land-
mass, reef, ships or other surface vessels
but can imply returns from sea surface
and clutter. As the level of clutter changes
with environment, the operator should
properly adjust the A/C SEA, A/C RAIN
and GAIN controls to be sure target
echoes are not eliminated from the
radar screen.
CAUTION
The plotting accuracy and response of
this auto plotter meets IMO standards.
Tracking accuracy is affected by the
following:
• Tracking accuracy is affected by course
change. One to two minutes is required to
restore vectors to full accuracy after an
abrupt course change. (The actual
amount depends on gyrocompass
specifications.)
• The amount of tracking delay is inversely
proportional to the relative speed of the
target. Delay is on the order of 15-30
seconds for high relative speed; 30-60
seconds for low relative speed.
Display accuracy is affected by the
following:
• Echo intensity
• Radar transmission pulsewidth
• Radar bearing error
• Gyrocompass error
• Course change (own ship or target)
CAUTION