User's Manual

5─53
5.3.9 Conditions for Deciding AIS Target to be Lost
About a lost target
When the data of an AIS target cannot be received for a specified time, the target is decided to be lost and the
target data is deleted. As shown in the table below, the time until target data is deleted varies depending on the
class of receive data and the target status.
Deciding AIS Target to be Lost
Time until data deletion
Target status
SOLAS ship
(Class A)
SOLAS ship
(Class B)
Vessel below 3 knots and it is now at anchor or on the berth
(Class B: below 2 knots)
18 min 18 min
Vessel of 3 knots or more and it is now at anchor or on the berth
60 sec 18 min
Vessel of 0 to 14 knots (Class B: 2 to 14 knots)
60 sec 180 sec
Vessel of 0 to 14 knots and it is now changing the course
60 sec 180 sec
Vessel of 14 to 23 knots
36 sec 180 sec
Vessel of 14 to 23 knots and it is now changing the course
36 sec 180 sec
Vessel of 23 knots or more
30 sec 180 sec
Vessel of 23 knots or more and it is now changing the course
30 sec 180 sec
SAR (Search and Rescue)
60 sec 60 sec
ATON (Aid to Navigation)
18 min 18 min
Base station
60 sec 60 sec
Reference:
• If Active targets (including dangerous ships) and numerically displayed targets is lost, a lost target alarm is
issued, and the symbol changes to a lost target symbol. The system continues to display the symbol where it
received the last data. If the ALARM ACK switch is pressed, the symbol is cleared.