Types of Automatic Identifications Systems

ITU-R Recommendation M.1371-1 describes the following types of AIS:

Class A

Shipborne mobile equipment intended for vessels meeting the requirements of IMO AIS carriage requirement.

Class B

Shipborne mobile equipment provides facilities not necessarily in full accord with IMO AIS carriage requirements. The Class B is nearly identical to the Class A, except the Class B:

• Has a reporting rate less than a Class A (e.g. every 30 sec. when under 14 knots, as opposed to every 10 sec. for Class A)
• Does not transmit the vessel’s IMO number
• Does not transmit ETA or destination
• Does not transmit navigational status
• Is only required to receive, not transmit, text safety messages
• Is only required to receive, not transmit, application identifiers (binary messages)
• Does not transmit rate of turn information
• Does not transmit maximum present static draught

U.S. Submission to the International Telecommunication Union: Document 8B/234-E, "PERFORMANCE ASSESSMENT AND INTEROPERABILITY OF PROPOSED CLASS B AIS WITH EXISTING CLASS A AIS SYSTEM USING SIMULATION SOFTWARE" (2005).

See a comparison of Class A and Class B/CS AIS.

Search and Rescue Aircraft

Aircraft mobile equipment, normally reporting every ten seconds.

Aids to Navigation

Shore-based station providing location of an aid to navigation.  Normally reports every three minutes.  This may eventually be used in lieu of racons.

Air Base Station

Shore-based station providing text messages, time synchronization, meteorological or hydrological information, navigation information, or position of other vessels.  Normally reports every ten seconds.

AIS Messages >>