Chapter 3: Using the AIS application 23
3.7 Using AIS for collision avoidance
Your AIS system can help with collision avoidance using the
following functions:
• Safe zones.
• Safety messages.
Safe zones
A safe zone is a red ring displayed on radar and/or chart pages
around your boat. Targets that come within this ring are consid-
ered dangerous.
An AIS safe zone uses the same criteria as MARPA to deter-
mine a targets status. A target is considered dangerous if it
comes within the CPA or TCPA of your boat. The CPA and
TCPA are calculated using COG/SOG and position from the AIS
target.
When your system recognizes a dangerous AIS target:
• The target symbol changes to red and flashes.
• An alarm pop-up is displayed.
• An alarm sounds.
With your AIS receiver connected and functioning, the system
continually checks for dangerous targets within the safe zone
and sounds an alarm if enabled, when necessary. However, the
dangerous target alarm operates irrespective of the AIS target
display or safe zone ring status.
To set up an AIS safe zone:
1. Select AIS Options
2. Press TARGET TRACKING. The AIS options soft keys
appear.
3. Press MARPA & AIS OPTIONS. The MARPA and AIS
options dialog box appears.
MARPA and AIS options
Parameter Options
(Default in bold)
Vector Length
The distance the vessel will travel
in the selected time period, at
current COG & SOG
0.5min, 1 min, 3 min,
6min, 12min, 30 min, 60
min
Target History
Plots a MARPA target’s previous
position at specified intervals. The
four most recent position points are
displayed. If True target vectors are
selected, the four most recent
vessel position points are also
displayed.
OFF, 0.5 min, 1 min, 3
min, 6 min
81286_2.book Page 23 Friday, December 5, 2008 2:29 PM
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