JRC JMR-5410-6XH - Danger Target Alarm (CPA;TCPA)

Section 6 Target Tracking and AIS 6-40
6.7.1 Danger target alarm (CPA/TCPA)
Since these alarms may include some errors depending on the target tracking
conditions, the navigation officer himself should make the final decision fo
r ship
operations such as collision avoidance.
Making the final navigation decision based only on the alarm may cause accidents
such as collisions.
In this system, targets are categorized into two types: tracked targets and dangerous targets
depending on the danger level. The danger level can easily be recognised on the display. So, it is
easily possible for the ship operator to judge which target is to be cautious about.
The danger target symbol of the tracked target will be displayed until either the tracking is stopped or
the conditions no longer apply.
The types of target and alarm are shown below.
Dangerous Target Alarm
Status
Symbol on
display
Alert
characters
Alarm sound Conditions
Tracked
target
Activated
AIS target
(Off) (Off)
• CPA > CPA Limit
• 0 > TCPA
• TCPA > TCPA Limit
The symbol is displayed
when one or more of the
above conditions are met.
Dangerous
target
Red blinking
CPA/
TCPA
Beep sound
(beep-beep-beep)
Alarm
acknowledgeable
• CPA≤ Limit
• 0≤TCPA≤
TCPA Limit
An alarm is issued when all
the conditions are met.
The sleeping AIS targets will
be activated.
CPA Limit and TCPA Limit: Setting Values
AIS12
12
AIS12
12