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What is AIS?

AIS, which stands for Automatic Identification System, is at its most basic level an electronic transponder installed on a boat or vessel that continuously transmits a VHF signal containing information including its name, call sign, type and position.  An AIS receiver mounted on another craft can then receive that information and use the signal to calculate and display the vessel's course and speed.  The end result is a display showing all AIS-enabled craft within VHF range, along with their course and speed.  AIS thus plays an invaluable role, particularly in areas of high traffic, to track the progress of other craft and thereby minimise the risk of collision.

While, at its most basic level, AIS can be installed simply to transmit the host vessel's call sign to alert other boats of its whereabouts, two-way AIS is generally preferred because it allows information to be exchanged between all AIS-enabled craft, maritime traffic stations, coastguard authorities and position-markers such as buoys and lighthouses. It is invaluable to navigators and on-watch crewmembers when making decisions about course and speed, determining the risk of collision and avoiding other hazards. AIS is also critical to marine search and rescue operations as it exactly pinpoints the position of the ship in distress, whether by day or night and in all conditions.

The central component of AIS is a transponder that automatically broadcasts information on the host vessel's position, speed and navigational status at regular intervals via a VHF transmitter. Received information about other AIS-transmitting boats is displayed on a screen or overlaid on a chartplotter, showing their call signs in real time and complementing the radar readout. The system can be programmed to track specific vessels so that navigational information can be exchanged automatically and remedial action taken if necessary to avoid a dangerous situation.

The International Maritime Organization requires that all ships of 300 tonnes or more, and all passenger ships regardless of size, are fitted with AIS. For recreational boats AIS is optional but becoming increasingly popular. Current worldwide usage of AIS is estimated to be more than 40,000 vessels.

Source: Simrad Yachting