Automatic Identification System (AIS)
A VHF transponder system that broadcasts a ship’s identity, position, course and speed for collision avoidance and tracking.
- Category
- Risk and Sanctions
- Abbreviation
- AIS
- Dictionary entry
- AIS
- Last reviewed
How it works
The Automatic Identification System (AIS) is a transponder that automatically broadcasts a ship’s identity (MMSI and often IMO), position, course, speed and voyage details over VHF, received by other ships, shore stations and satellites. SOLAS requires it on most commercial vessels for safety and collision avoidance.
Because the signal can be received globally, AIS is also the backbone of commercial vessel tracking. A deliberate AIS gap, switching off the transponder, is a classic evasion tactic and one of the strongest signals in dark-fleet and sanctions screening.
Where it shows up on The Maritime
Also known as: AIS, automatic identification system, transponder.
The short dictionary definition is at Dictionary entry: AIS. This page is the explainer.
Related terms
Dark Fleet
The population of ageing, opaquely owned and often uninsured tankers that move sanctioned oil while disguising their movements.
AIS Spoofing
The falsification of a ship’s broadcast position or identity on AIS to disguise where she really is or what she really is.
Ship-to-Ship Transfer (STS)
The transfer of cargo directly between two vessels moored alongside, often at anchor or offshore rather than at a terminal.
Maritime Mobile Service Identity (MMSI)
A nine-digit number identifying a ship’s radio station, used by AIS and distress systems; distinct from the permanent IMO number.
More risk and sanctions terms
A plain-English reference definition: our own explanation of a standard shipping concept, not a licensed source or legal advice. See the full glossary or the broader maritime dictionary.
Last reviewed: .