Arpa Operation; How To Show Or Hide The Arpa Display; Specifications - Furuno MFD12 Operator's Manual

6.27

ARPA Operation

The ARPA (Automatic Radar Plotting Aid) shows the movement of a maximum of 30
radar targets. The targets can be acquired manually or automatically. All 30 targets
can be acquired manually when the ARPA acquisition area is not active. If the ARPA
acquisition area is active, that total is equally divided between manual and auto acqui-
sition.
ARPA requires speed and heading data.
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 Sea, Rain and Gain
to be sure target echoes are not elimi-
nated from the radar screen.
6.27.1

How to Show or Hide the ARPA Display

1. On the chart plotter or radar display, long-push the RotoKey.
2. Use the RotoKey to select [Targets] followed by ARPA.
3. Push the RotoKey to show or hide the ARPA display.
WARNING WARNING CAUTION 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)
6. Radar
6-29