Page 71 - Electronic Navigation Cyber Book

The original purpose of AIS was solely collision avoidance but many other
applications have since developed and continue to be developed. AIS is
currently used for:

Collision avoidance
AIS was developed by the IMO technical committees as a technology to
avoid collisions among large vessels at sea that are not within range of
shore-based systems. The technology identifies every vessel
individually, along with its specific position and movements, enabling a
virtual picture to be created in real time. The AIS standards include a
variety of automatic calculations based on these position reports such as
Closest Point of Approach (CPA) and collision alarms. As AIS is not used
by all vessels, AIS is usually used in conjunction with radar. When a ship
is navigating at sea, information about the movement and identity of other
ships in the vicinity is critical for navigators to make decisions to avoid
collision with other ships and dangers (shoal or rocks). Visual observation
(e.g., unaided, binoculars, and night vision), audio exchanges (e.g.,
whistle, horns, and VHF radio), and radar or Automatic Radar Plotting
Aid are historically used for this purpose. These preventative
mechanisms, however, sometimes fail due to time delays, radar
limitations, miscalculations, and display malfunctions and can result in a
collision. While requirements of AIS are to display only very basic text
information, the data obtained can be integrated with a
graphicalelectronic chart or a radar display, providing consolidated
navigational information on a single display.
Fishing Fleet Monitoring and Control
AIS is widely used by national authorities to track and monitor the
activities of their national fishing fleets. AIS enables authorities to reliably
and cost effectively monitor fishing vessel activities along their coast line,
typically out to a range of 60 miles (depending on location and quality of
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