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5.3.8 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 (Class A) or 2 knots (Class B) and it is
now at anchor or on the berth
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
ATON (Aids to navigation)
18 min 18 min
Reference:
When a dangerous target ship is lost, a lost alarm is issued and the symbol changes to a lost
symbol. The system calculates the current position from the last-received data and continues
displaying the symbol for eternity.
If the [ALARM ACK] key is pressed, the symbol is cleared.
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