The AIS System
Posted on Marine equipment
The AIS system (Automatic Identification System) helps boaters avoid collisions and assists commercial vessel traffic centers as they direct freighters, cargo ships, tankers, and passenger vessels through heavily-traveled commercial ports such as New York Harbor and Galveston Bay.
Ships and private powerboats and sailboats equipped with AIS transponders continually transmit data that includes their exact position, their course and speed, and their vessel name via VHF radio-based transmitters. These signals can be picked up by anyone with an AIS receiver that is within range of the VHF radio transmission — generally those within about 15 to 20 miles.
Prior to the advent of AIS (which sometimes is mistakenly called the Automated Identification System), this information was available only to U.S. Coast Guard Vessel Traffic Service (VTS) operations. VTS operations monitor vessel movements within specific VTS areas, exchange information regarding vessel movements, and provide advisories to vessel masters.
Now, almost all large commercial ships (those over 300 gross tons) must carry marine AIS Class A transponders, while marine AIS Class B transponders are optional equipment for private vessels.
Since its advent less than a decade ago, AIS has played an important national security role by making it possible for Coast Guard officials to identify vessels by name and track their movements within crowded harbors, and it also has made tracking ship positions worldwide possible with free AIS services.