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.
The Coast Guard published rules in 2003 that phased in requirements for commercial ships to carry Class A AIS transponders.
Class A AIS Transponders Broadcast Data Six Times a Minute
Coast Guard-approved Class A AIS units broadcast critical information data every two to 10 seconds, including the ship's unique identification number, position, navigation status (i.e., "under way using engine" or "at anchor"), rate of turn, and speed over ground.
Every six minutes, marine AIS Class A units broadcast less-critical information, including the ship's name, type of cargo, dimensions, draft, destination, and estimated time of arrival at the destination.
Class A marine AIS transponders meet strict Coast Guard and international rules governing operation and backups in the case of marine electronics failure. Consequently, the units cost far more than Class B marine AIS transceivers used on private sailboats and power boats.
For example, the Furuno USA FA150 Class A unit lists for $4,495, while the ACR Electronics GlobalWatch Universal Automatic Identification System sells at discount for about $4,100.
Coast Guard Rules Require Near-Universal Marine AIS Coverage
Virtually all large commercial ships operating internationally and many operating in United States waters only must carry Class A AIS transponders. These Coast Guard regulations cover:
- Self-propelled vessels 65 feet or more in commercial service and on an international voyage, except for passenger and fishing vessels
- Passenger vessels that are 150 gross tons or more
- All tankers, regardless of tonnage
- All other commercial vessels that are 300 gross tons or more
In addition, certain vessels navigating specified harbors with heavy commercial traffic must carry a marine AIS Class A transponder. These include:
- Self-propelled commercial vessels of 65 feet or more in length, other than fishing vessels
- Commercial towing vessels of 26 feet or more in length and more than 600 horsepower
- Passenger vessels approved to carry more than 150 passengers-for-hire
The Coast Guard also has proposed new AIS rules that would expand requirements to all U.S. navigable waters. These proposed Coast Guard rules also would expand AIS carriage requirements to: commercial vessels carrying 50 or more passengers; fishing vessels 65 feet or greater in length; high-speed passenger vessels; dredges and floating plants operating in or near channels or fairways; and vessels carrying or moving certain dangerous cargo.
Marine AIS Class A Transponders Must Transmit Continuously
The Coast Guard's rules don't just require that commercial vessels carry Class A AIS transponders; the units must be properly installed, function properly and transmit continuously.
The rules allow only one exception to this requirement: "Should continual operation of AIS compromise the safety or security of the vessel or where a security incident is imminent, the AIS may be switched off. This action and the reason for taking it must be reported to the nearest U.S. Captain of the Port or Vessel Traffic Center and recorded in the ship's logbook. The AIS should return to continuous operation as soon as the source of danger has been mitigated. "
Ships experiencing malfunctions of their shipboard AIS units must report the problem to the nearest VTS operations center.
Jane Anderson - Jane M. Anderson spends as much time as possible on the water, working and sailing on boats. She grew up sailing Sunfish and Rhodes 19s on ...
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