Marine Glossary

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AIS

An integrated system of GPS receiver, display module, and short-range radio transceiver. Vessels equipped with AIS continuously broadcast their position and present motion along with their identity and intended route, while receiving the same signals from other vessels in the region. The accumulated data from all vessels can be presented on an electronic chart system (ECS) so relative courses can be easily evaluated. There is a class A and class B standard, which differ notably in their specifications.

Receivers alone (as opposed to transceivers) show you other vessels, but do not broadcast your information. At $280 or so for a standard unit. A basic AIS receiver should be considered minimum equipment for all vessels. Transievers cost 3 or 4 times as much.

Starpath offers a unique portable the dAISy. Very small and inexpensive. Ideal for small boats or backup for any voyage, or for chartering.

On larger vessels, the system is typically used in conjunction with ARPA and ECDIS. Some AIS systems, however, are text based without an ECS display since that meets the AIS carriage requirements. See ARPA, ECDIS.

The primary reference is the USCG NavCen section on AIS.

The wiki has a good overview of the system.

We have a short article for mariners online Introduction to AIS.

Note that cell phone apps that show AIS targets can often be much delayed compared to your own measurements... to the point of being a hazard rather than a help in some circumstances. There are, however, very small units for $60 that can be read in a mobile app charting program that will do the job for targets within 5 miles or so. See last link above.

See also AIS voyage data, AIS dynamic data, and AIS static data.