AIS stands for Automatic Identification System, a marine system which identifies a ship to others in its immediate vicinity. It does that by continually transmitting a ship’s position, course and call sign on dedicated VHF radio channels.
The information of adjacent ships is picked up by the receiver section of an AIS transponder (or dedicated AIS receiver) and can conveniently be displayed on a chart plotter or other display device. The system has been mandatory on commercial shipping (over 300 ton) since 2004. In recent years,a version (AIS class B) has become available for leisure craft and other non-SOLAS vessels.
When venturing into major shipping lanes or passing busy ports, it ranks as essential safety equipment for cruising boats. With lower cost class B equipment, it is now practical to equip cruising yachts and fishing boats with AIS transponders. That will be invaluable when visibility is poor and at night. And, as adoption increases, there is a real opportunity for wider applications such as keeping track of a cruising boat by family and friends through the use of repeater stations and tracking websites like Marine Traffic
Rather than explain AIS in all its intricacies here are some links which describe most aspects of AIS.
- This PDF by Digital Yacht has an excellent overview of AIS
- The Wikipedia entry for AIS describes much of the detail, although it is a bit “light on” regarding Class B systems for recreational vessels.
- The US Coast Guard has an excellent set of AIS pages explaining most aspects of the system.
- Bosun’s Mate provides a concise technical description.