AIS aid to navigation

An AIS aid to navigation (AIS AtoN) is a navigation mark whose position and status are broadcast over the Automatic Identification System, transmitted as ITU-R M.1371 Message 21. Three types exist: physical AIS AtoN fitted to a real buoy or beacon, synthetic AIS AtoN broadcast from a shore station to represent a real mark, and virtual AIS AtoN that has no physical structure at all, useful for marking a new wreck before a buoy can be laid. IALA Recommendation R1001 and the AIS AtoN guidance govern symbol, name, and type-code use. The mark appears on AIS-capable ECDIS and plotters with its charted symbol, supplementing but not replacing the visual or radar aid.