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AIS Information

What is AIS?

AIS stands for Automatic Identification System.  It is a maritime navigation safety communications system that provides vessel information, including the vessel's identity, type, position, course, speed, navigational status and other safety-related information automatically to appropriately equipped shore stations, other ships, and aircraft; receives automatically such information from similarly fitted ships; monitors and tracks ships; and exchanges data with shore-based facilities.  Depending on how the navigation equipment is set up, information can be viewed on radars, chart plotters etc.  Follow this Link to learn more. 

Why should my vessel be fitted with AIS?

In Bermuda your AIS equipped vessel will always be visible to Bermuda Radio as well as other commercial marine traffic and suitably fitted private vessels within VHF radio range.  Although primarily a navigational aid, AIS can prove vital in emergency situations when a vessel requires assistance.  

What else do I need if installing an AIS unit on my vessel?

In order to work, all AIS transceiver units must be programmed with a valid MMSI (Maritime Mobile Service Identity) number, which is a unique 9 digit number assigned to your vessel as part of its Class 5 Radio Licence issued by the Regulatory Authority of Bermuda.   The MMSI is similar to a phone number for the ships radio and can be used to place a radio call to a particular vessel. AIS systems also use MMSI numbers to identify vessels.  With the exception of an AIS-SART, the same MMSI is used for all radio equipment on a vessel, so the AIS should be programmed with the same MMSI as the VHF radio.

What kinds of AIS devices are there in use?

Class A transceivers: These are designed to be fitted to commercial vessels such as cargo ships and large passenger vessels. Class A transceivers transmit at a higher VHF signal power than class B transceivers and therefore can be received by more distant vessels, and also transmit more frequently. Class A transceivers are mandatory on all vessels over 300 gross tonnes on international voyages and certain types of passenger vessels under the SOLAS mandate.

Inland AIS stations: Similar to class A transceivers with additional features for use on Inland waterways.

Class B transceivers: Similar to Class A transceivers in many ways, but are normally lower cost due to the less stringent performance requirements. Class B transceivers transmit at a lower power and at a lower reporting rate than Class A transceivers.

AIS base stations: AIS base stations are used by Vessel Traffic Services to monitor and control the transmissions of AIS transceivers.

AIS Aids to Navigation (AtoN):

Real AIS AtoN - A physical aid to navigation structure on which an AIS transmitter is affixed and from which AIS messages are broadcast.

Synthetic AIS AtoN - A physical aid to navigation structure, without an AIS transmitter, but for which AIS messages are broadcast from another (usually land-based) location.

Virtual AIS AtoN - An aid to navigation with no physical structure. It exists only through AIS messages broadcast from another location. Uses of virtual AtoNs include situations where a marker needs to be placed quickly, such as to mark a newly identified isolated danger or wreck, or in circumstances where a physical AtoN cannot be established. These aids can only be seen on an Electronic Chart Display and Information System (ECDIS), or other AIS enabled display, such as a ship’s radar.

AIS receivers: AIS receivers receive transmissions from Class A transceivers, Class B transceivers, AtoNs and AIS base stations but do not transmit any information about the vessel on which they are installed.

What are AIS tracking websites and how do they work?

AIS Tracking Websites have become a very popular and useful tool.  Sites such as (which has coverage in Bermuda) offer a free service where web users can search for vessels around the world and see the current vessel traffic in most areas depicted on maps or old satellite images.

There are occasions when a vessels AIS signal may not be appearing on these websites, but before you worry that your AIS transceiver is not working correctly, the following should be considered:

Coverage: Not all AIS websites offer complete coverage, so there is a chance that you may be out of range of a receiving station for that site or that receiving stations may be offline.  In Bermuda, these land based receiving stations are operated by private citizens and therefore coverage can vary.   

Antenna setup: If you are being seen by other vessels around you, but not by the AIS website, then the issue could also be associated with your choice/installation of VHF antenna.  If in doubt, refer to the user manual for advice or contact us for help.

Unit configuration: Make sure that your AIS transceiver is correctly setup with the complete vessel details and that it is connected to a GPS antenna, as per the user instructions.

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