About AIS

About AIS

The Automatic Identification System (AIS) is a positioning and ship information reporting system. It enables AIS-equipped ships to automatically and dynamically share and regularly update their position, speed, heading and other information, such as ship identification numbers, with similarly equipped ships. Positioning is provided by the Global Positioning System (GPS) and communication between ships is achieved through very high frequency (VHF) digital transmission.

There are many types of AIS equipment, such as:

Class A transceivers. Type A transceivers transmit VHF signals at a higher power than Type B transceivers and can therefore be received by ships at greater distances and transmit more frequently. According to the SOLAS Convention, all international ships over 300 gross tons and certain types of passenger ships must be equipped with a Class A transceiver.

Class B transceivers. Similar in many respects to a Class A transceiver, but usually less costly due to less stringent performance requirements, Class B transceivers transmit at lower power and reporting rates than Class A transceivers.

AIS Base Stations. AIS base stations are used by ship traffic systems to monitor and control the transmission of AIS transceivers.

Aids to Navigation (AtoN) transceivers. AtoN transceivers are mounted on buoys or other shipping hazards and are used to transmit position details to surrounding vessels.

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