Furuno FEA-2107 Operator's Manual page 376

21. AIS Target Functions
The operator can set Closest Point of Arrival (CPA), and Time for CPA (TCPA) to define dangerous AIS targets.
CPA and TCPA limits are common for ECDIS display and danger target log function of ARPA and AIS targets. The
ECDIS display shows a dangerous AIS target with its symbol blinking, in green and red alternately.
Note that the CPA and TCPA limits are only for ECDIS. ARPA
radar has its own setting for dangerous targets and thus a target
which is dangerous on the ARPA display can be safe on ECDIS
and vice versa. If an ARPA target is within the CPA and TCPA
settings, it is shown as a dangerous ARPA target on the ECDIS
display. Log interval defines time period for logging.
If an AIS target locates within the CPA and TCPA values, it is shown as a dangerous AIS target on the ECDIS
display. Note that the same situation occurs with ARPA targets.
Note1: If own ship position is based on Dead Reckoning, then CPA/TCPA and BCR/BCT values are not calculated
and not displayed.
Note2: If TCPA has a negative value it means that you have already passed the closest point and the AIS target is
going away form own ship.
21-6
True Vect(G) 12 nm
Past PosnTrue 2 min
CPA 1.5 nm 10 min