AIS (Automatic Identification System) technology offers a range of safety-related options for mariners. AIS displays provide near real time information about ships, navigational aids, and other structures. The use of AIS technology can result in improved navigational safety, greater situational awareness, and other benefits.

The U.S. Coast Guard provides the following explanation of AIS technology: “AIS is a maritime navigation safety communications system standardized by the International Telecommunication Union (ITU) and adopted by the International Maritime Organization (IMO) 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.”

AIS components include transponders, receivers, and other devices that operate in the VHF mobile maritime band.

The U.S. Coast Guard has developed rules that require owners and operators of most commercial vessels operating on U.S. navigable waters to be outfitted with an Automatic Identification System (Class A or B). Ships equipped with AIS usually broadcast information including call sign, heading, position (latitude and longitude), speed over ground, and rate of turn.

AIS devices must be operated with an official 9-digit Maritime Mobile Service Identity (MMSI) number assigned to the vessel and its owner.

AIS aids to navigation (ATON) consist of shore-based or mobile stations that provide location and status. ATONs may also broadcast application specific messages. In the United States, ATON stations are identified by a 993xxxxxx MMSI; and, are listed in the USCG Light List.

Shore-based AIS base stations broadcast identity, time synchronization, text messages, and other information. Identified by a 00MIDxxxxx MMSI, shore-based stations can also transmit AIS ATON Reports (message 21) and Application Specific Messages (ASM) for meteorological or hydrological information, marine safety information, etc. U.S. shore-based stations that also act as AIS ATONs or transmit ASMs are denoted in the Coast Guard Light List.

Portable devices called AIS search and rescue transmitters (AIS-SART) can be used to provide positional information from survival craft.

AIS Applications

AIS technology is often used by mariners for monitoring vessel traffic, identifying aids to navigation, and other needs. Electronic devices overlay AIS data on digital chart displays, either alone or combined with radar or other data.

A wide range of online tracking tools are also available for mariners. Commercial AIS tracking services offer limited free features or paid subscriptions with added features. Online AIS trackers usually provide information including vessel identity (MMSI), type, position, course, speed, navigational status, and other data. Vessel tracking tools are used by fleet managers, search and rescue personnel, boaters, researchers, and other stakeholders.

U.S. Coast Guard Vessel Traffic Services (VTS) ashore use AIS to identify, locate, and monitor vessels. In the Mid Atlantic region, the USCG Sector New York VTS control center coordinates vessel traffic movements through the ports of New York and New Jersey.

Related Information

Marine Electronics