AIS (Automatic Identification System)
AIS (Automatic Identification System) is the maritime tracking system that broadcasts a vessel's identity, position, speed, and course to other AIS-equipped ships and shore stations. SOLAS requires AIS on commercial vessels over 300 GT. It is standard on superyachts and larger private yachts for safety and traffic management.
Definition
Semantic definition
- Subject
- AIS
- Predicate
- is the maritime tracking system that
- Object
- broadcasts vessel identity, position, speed, and course to other ships and shore stations for collision avoidance and traffic management.
AIS is the maritime tracking system that broadcasts vessel identity, position, speed, and course to other ships and shore stations for collision avoidance and traffic management.
What is AIS?
AIS (Automatic Identification System) is the international maritime tracking system that continuously broadcasts a vessel's identity, position, speed, course, and status to nearby AIS-equipped vessels and shore-based AIS receivers. Developed by the IMO and mandatory under SOLAS for all vessels over 300 GT on international voyages, vessels over 500 GT on domestic voyages, and all passenger vessels, AIS has become the standard situational awareness tool in commercial maritime operations. Superyachts typically carry Class A AIS transponders, while smaller yachts may carry Class B. AIS data is received by vessel and coastal networks and aggregated by commercial platforms (MarineTraffic, VesselFinder) for global tracking.
Class A vs Class B AIS
Two main classes of AIS transponder are used on yachts.
Class A AIS
Required by SOLAS for vessels over 300 GT on international voyages and all passenger vessels. Transmits at higher power (12.5W), updates position more frequently (every 2-10 seconds when underway), and includes voyage-specific data (destination, ETA, navigational status). Class A has display and keyboard requirements. Mandatory on all superyachts above SOLAS thresholds.
Class B AIS
Used by smaller recreational and commercial vessels not subject to SOLAS AIS carriage requirements. Lower power (2W), less frequent updates (every 30 seconds underway), does not transmit destination or ETA. Less visible to commercial traffic in high-density areas. Adequate for coastal and offshore yacht operations not requiring full SOLAS compliance.
AIS for Collision Avoidance
AIS supplements radar for situational awareness and collision avoidance but does not replace the watchkeeper's visual lookout (COLREGs Rule 5) or radar. AIS provides: vessel identity (name, MMSI, call sign); type of vessel; exact position with GPS accuracy; speed over ground and course over ground; navigational status (underway, at anchor, not under command); and rate of turn. This data allows the officer of the watch to identify vessels, calculate closest point of approach (CPA), and take informed action. AIS targets on ECDIS or chart plotter must be cross-checked with radar and visual contact — AIS can be switched off or corrupted.
AIS Security Considerations
AIS data is publicly broadcast on VHF frequencies and aggregated on commercial platforms accessible to anyone worldwide. This creates privacy and security concerns for high-profile yacht owners. Options for managing AIS visibility: some flag states allow AIS to be switched off or anonymised for security reasons (the master must log this decision and report to the coast guard as required); some owners operate under charter name rather than vessel name; AIS Class B transponders have lower range and are less visible on aggregation platforms. Switching off AIS without authorisation is a SOLAS violation and a COLREGs hazard.
AIS Maintenance and Registration
AIS transponders must be registered with a unique MMSI (Maritime Mobile Service Identity) number associated with the vessel's flag state. The MMSI is cross-referenced with vessel identity on GMDSS and SOLAS databases. AIS must be serviced as part of the vessel's PMS — annual inspection by a certified GMDSS engineer is standard practice. Incorrect MMSI numbers, unregistered AIS, or AIS transmitting incorrect vessel data are PSC deficiencies.
Frequently Asked Questions
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