Navigation Center Website Top Header Banner
Skip Navigation Home | DGPS Advisories | GPS Constellation Status | MSI Data Downloads | GPS Testing Notices | LNMs | Almanacs | Nav Rules | AIS | N. Amer. Ice Svc | Contact Us | Search
Automatic Identification System
Mission Areas
Subscribe / Report (free)
Maritime Information
TYPES OF AUTOMATIC IDENTIFICATION SYSTEMS (PER ITU-R M.1371 AND IEC STANDARDS)

Class A (IEC 61993-2)

Shipborne mobile equipment intended to meet the performance standards and carriage requirements adopted by IMO. Class A stations report their position (message 1/2/3) autonomously every 2-10 seconds dependent on the vessel’s speed and/or course changes (every three minutes or less when at anchor or moored); and, the vessel’s static and voyage related information (message 5) every 6 minutes. Class A stations are also capable of text messaging safety related information (message 6/8) and AIS Application Specific Messages (message 6,8,25,26), such as meteorological and hydrological data, electronic Broadcast Notice to Mariners, and other marine safety information (see IMO Safety of Navigation Circular 289, GUIDANCE ON THE USE OF AIS APPLICATION-SPECIFIC MESSAGES (ASM) or the IALA Application Specific Message Collection).

Class B (IEC 62287-1 and 62287-2)

Shipborne mobile equipment which is interoperable with all other AIS stations, but, does not meet all the performance standards adopted by IMO. Similar to Class A stations, they report every three minutes or less when at anchor or moored, but, their position (message 6/8) is reported less often and at a lower power.  Likewise, they report the vessel’s static data (message 18/24) every 6 minutes, but, not any voyage related information. They can receive safety related text and application specific messages, but, cannot transmit them.
There are two types of Class B AIS, those using carrier sense Time-Division Multiple Access (CS-TDMA) technology and those like the Class A using Self-Organizing Time-Division Multiple Access Technology (SO-TDMA).  Class B/SO is generally more capable; Class B/CS is generally less expensive. See this broader comparison of Class A and Class B AIS.

Search and Rescue Aircraft (IEC standards yet to be developed)

Aircraft mobile equipment, normally reporting every ten seconds.

AIS Aid to Navigation (IEC 62320-2)

Shore-based or mobile station providing location and status of an aid to navigation (ATON). Normally reports (message 21) every three minutes or less. These stations may also broadcast Application Specific Messages (message 6/8). Federal AIS ATON Stations and the messages they broadcast are listed in the USCG Light List.

Note, current U.S. regulations (33 CFR §66.01-1) prohibit the authorization of electronic aids to navigation (ATON) as private aids--other than racons or radars. The Coast Guard is in the process of amending these regulations to permit the authorization and use of AIS ATON's as private aids to navigation; until this accomplished the Coast Guard will not be accepting or approving any private (non-Federal) USCG AIS Aton Applications. Further, the Federal Communications Commission (FCC) will not grant licensing to an AIS ATON station without prior approval from the Coast Guard.

Coast Guard Special Notice regarding their use of AIS ATONs.

AIS Search and Rescue Transmitter (SART) (IEC 61097-14)

Mobile equipment to assist homing to itself (i.e. life boats, life raft). An AIS SART transmits a text broadcast (message 14) of either 'SART TEST' or 'ACTIVE SART'. When active the unit also transmits a position message (message 1 with a 'Navigation Status' = 14) in a burst of 8 messages once per minute.
  • AIS SARTs are also used in maritime survivor locating devices (MSLD) or man overboard (MOB) devices, as specified in RTCM 11901.1, Standard for Maritime Survivor Locating Devices as well as for AIS locating beacons on 406 MHz EPIRBs.  Standard AIS SARTs can be identified by MMSI's beginning with the numbers "970", AIS maritime survivor locating devices or MOBs with MMSIs beginning with "972", and AIS EPIRB with MMSIs beginning with "974".  All categories of AIS SARTs will be displayed on IMO-mandated shipboard navigation displays.
AIS Base Station (IEC 62320-1)

Shore-based station providing text messages, time synchronization, meteorological or hydrological information, navigation information, or position of other vessels. Normally reports (message 4) every ten seconds. Note: private sale or operation of an AIS Base Station is prohibited in the United States (47 CFR 2.803, 80.371).

For a listing of U.S. certified AIS equipment visit the Coast Guard Maritime Information Exchange (CGMIX) (go to’ EQList Search’, select “Approval Series Name: Shipborne AIS”) or the FCC OET Equipment Authorization Search Form (select " Equipment Class: AIS”). Certification requirements for Class A AIS are described in 47 CFR 80.275, 47 CFR 80.1101(c)12 and in the Coast Guard's Navigational and Vessel Inspection Circular (NVIC) 8-01, as amended by Change 01, Approval of Navigation Equipment for Ships. NVIC 8-01 describes the certification process for AIS and other navigation equipment denoted in SOLAS V. Further, neither the National Telecommunication Information Agency (NTIA) or Federal Communications Commission (FCC) will grant AIS ATON station authorization without prior approval from the Coast Guard. For further information on AIS ATON see the International Association of Lighthouse Authorities various publications on the subject.

You may also download Data Broadcasted From Each AIS Station Type.