VHF transponder system that automatically broadcasts vessel identity, position, course, and speed to nearby ships and shore stations.
Quick facts
Regulation
SOLAS Chapter V
Regulation
COLREGs Rule 7
In practice
On the bridge, the OOW uses AIS data overlaid on the radar or ECDIS to identify vessels, assess collision risk, and coordinate manoeuvres by VHF. AIS is not a substitute for radar watchkeeping: targets may be lost in clutter, vessels may have switched off their transponders, or data may be inaccurate due to GPS errors or deliberate falsification. COLREGs Rule 7 requires all available means to determine collision risk; AIS is one such means but must be cross-checked against visual observation and radar. IMO MSC.1/Circ.1310 reminds operators that AIS information should not be accepted uncritically.
Regulatory detail & full definition
The Automatic Identification System (AIS) is a VHF transponder system that broadcasts a vessel's identity (MMSI, name, call sign, and IMO number), position, course over ground, speed over ground, rate of turn, navigational status, and destination to other vessels and shore stations. SOLAS Chapter V, Regulation 19 mandates Class A AIS on all ships of 300 GT and above on international voyages, on cargo ships of 500 GT and above, and on all passenger ships. Transmissions are received and decoded by nearby vessels and by AIS base stations, which feed vessel traffic services and maritime rescue coordination centres.
On the bridge, the OOW uses AIS data overlaid on the radar or ECDIS to identify vessels, assess collision risk, and coordinate manoeuvres by VHF. AIS is not a substitute for radar watchkeeping: targets may be lost in clutter, vessels may have switched off their transponders, or data may be inaccurate due to GPS errors or deliberate falsification. COLREGs Rule 7 requires all available means to determine collision risk; AIS is one such means but must be cross-checked against visual observation and radar. IMO MSC.1/Circ.1310 reminds operators that AIS information should not be accepted uncritically.