AIS — what it is
The Automatic Identification System (AIS) is a ship-borne transponder that broadcasts position, speed, heading, vessel name, IMO number, and cargo type. AIS is intended for collision avoidance; the data is collected by terrestrial and satellite receivers and is publicly accessible through services like MarineTraffic and VesselFinder.
What AIS shows well
- Vessel movements through chokepoints (Hormuz, Bab el-Mandeb, Suez, Malacca).
- Route changes in response to incidents.
- Convoys, anchor patterns, and port loitering.
- Ship-to-ship transfers in known sanctions-evasion zones.
Limits
- AIS transponders can be turned off ("going dark"). Absence of signal is not absence of vessel.
- AIS data can be spoofed — false position broadcasts are a documented sanctions-evasion technique.
- Cargo declarations are self-reported.
- Beneficial ownership is often opaque even when the vessel is fully transparent.