Users Manual Part 6

4. AIS OPERATION
4-20
4.13 AIS Collision Alarm (CPA, TCPA)
This radar calculates CPA and TCPA by using own ship and relative target positions.
An AIS dangerous target is one whose CPA and TCPA are within the range of the CPA
and TCPA limits set in the TT/AIS box. The AIS symbol of an AIS dangerous target is
red and flashing, and is announced with the Alert "AIS DANGER OF COLLISION". Af-
ter the alert is acknowledged the target symbol is displayed in red color.
4.13.1 How to set CPA and TCPA
The CPA/TCPA function can be activated and deactivated from the [CPA/TCPA] box
at the bottom-right of the screen.
1. Left-click the [CPA/TCPA] indication to activate the feature.
Click the indication to toggle between active (settings are visible and can be
changed) and inactive (indication shows "OFF").
Note: The [CPA/TCPA] indication is hidden when [SIMPLE] display mode is used.
To change the setting in [SIMPLE] mode, first restore [NORMAL] display mode,
adjust the setting, then return to [SIMPLE] mode. See section 1.9 for how to
change the display mode.
2. Place the cursor on the indication you wish to adjust.
3. Left-click, or spin the scrollwheel, to adjust the settings as required. The settings
options are outlined in the table below.
Indication Method Settings options
CPA Left-click 0.5, 1, 1.5, 2, 3, 4, 5, 6 (NM)
Scrollwheel 0.1 to 20; 0 to 10 in 0.1 NM increments, 1 NM increments thereafter
TCPA Left-click 1, 2, 3, 4, 5, 6, 12, 15 (minutes)
Scrollwheel 1 to 60 minutes in 1-minute increments
Thicker than
activated target
When a sleeping or an activated target violates the CPA/TCPA
alarm setting its symbol changes to the dangerous target
symbol (red and flashing) and the message “AIS DANGER OF
COLLISON” appears. To acknowledge the CPA/TCPA alarm,
press the ALARM ACK key, click the [ALERT] box, or click the
CPA/TCPA alarm in the ALERT LIST. The audible alarm is
silenced and the symbol stops flashing.
Take appropriate action to avoid collision.
Dangerous target
CPA setting
TCPA setting
Left-click here to activate/deactivate
the CPA/TCPA settings.