Other information broadcast by the AIS is electronically obtained from shipboard equipment through standard marine data connections.Īlthough only one channel is necessary, each station transmits and receives over two radio channels to avoid interference and communication loss from ships. Position and timing information is normally derived from an integral or external GPS receiver. The AIS system consists of one VHF transmitter, two VHF TDMA receivers, one VHF DSC receiver, and a standard marine electronic communications link to shipboard display and sensor systems. This meant ships could sail as far as they liked, and we’d always have peace of mind knowing exactly where they were and how they were doing. As ships began sailing further away from land, they started sending the signal to low orbit satellites, relaying information back to land. Originally, AIS was used terrestrially, meaning the signal was sent from the boat to land and had a range of roughly 20 miles (also considering the earth’s curvature). How does AIS work exactly? How do we obtain all this data? This frequency limits the line of sight, which is about 40 miles.

It uses Self Organizing Time Division Multiple Access (STDMA) technology to meet the high broadcast rate.

AIS 2: 162.025 MHz- Channel 88B (Duplex for the ship to shore).

AIS 1: Works on 161.975 MHz- Channel 87B (Simplex, for the ship to ship).Primarily used for vessels such as pleasure craftsĪIS operates principally on two dedicated frequencies or VHF channels: Class B: Provides limited functionality and is intended for non-SOLAS vessels.Class A: Mandated for all vessels 300 GT and above engaged on international voyages as well as all passenger ships.The IMO Convention for the Safety Of Life At Sea (SOLAS) Regulation V/19.2.4 requires all vessels of 300 GT and above engaged on international voyages and all passenger ships, irrespective of size, to carry AIS onboard. The Panama Canal uses the AIS to provide information about rain along the canal and wind in the locks. Vessel Traffic Services (VTS) ashore use AIS to identify, locate and monitor vessels. However, it is only an aid to navigation and should not be used for collision avoidance.

It is fitted on ships for the identification of ships and navigational marks.

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