User's Manual

AIS Class B Transceiver
62
7.2 Collision Alarm – CPA/TCPA
This is a Level 1 alarm. If you have activated the CPA/TCPA Alarm from
within the Alarm Setup Menu, the CPA/TCPA is then calculated from the
received position, COG and SOG of the AIS transmissions, from all AIS
equipped vessels in your VHF range.
Note CPA – “Closest Point of Approach” is the calculated distance of how
close a vessel will pass.
TCPA – “Time to Closest Point of Approach” is the calculated time to
reach the CPA.
The CPA/TCPA alarm values are set by the user, as described in section
5.5.1.1.
WARNING
It is the responsibility of the user to determine how close
another vessel may pass without being dangerous, and
how quickly the user can react to manoeuvre their own
vessel in order to avoid a collision.
If both values calculated by the AI50 are less than, or equal to the values
set by the user, then an alarm will activate, regardless of what screen the
unit is in. An audible alarm will sound and a window will open displaying
the following information Fig. 7.1.
Because this information is live, it is continuously being recalculated and
updated.
To confirm and clear this alarm, press ◄, this will close the window and
return you to current display.
Fig. 7.1 – CPA/TCPA Alarm