The Automatic Identification System (AIS) is an automatic tracking system that uses transponders on ships and is used by Vessel Traffic Services (VTS) to determine ship position. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport.

The IMO's Convention for SOLAS vessels requires AIS equipment to be fitted onboard ships with 300 or more gross tonnage, and all passenger ships regardless of size.