Aids To Navigation
AIS for Aids to Navigation (AtoNs)
AIS transmitters enhance navigation safety by broadcasting precise position and identification details from fixed or floating Aids to Navigation (AtoNs), such as buoys, beacons, or lights. This AIS data allows mariners to confirm their vessel’s position, recognize navigational aids well before they're visible visually or by radar, and plan maneuvers accordingly.
Types of AIS AtoNs
There are three distinct types of AIS-equipped AtoNs, each with specific applications:
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Real AIS AtoN
A physical aid to navigation equipped with its own AIS transmitter that broadcasts its exact location and identification directly. -
Synthetic AIS AtoN
A physical navigational aid without its own transmitter. AIS messages for these aids are broadcast remotely from a land-based station, accurately representing the aid's location on electronic navigation systems. -
Virtual AIS AtoN
A navigational marker that exists only digitally through AIS broadcasts, with no physical structure. Virtual AIS AtoNs are ideal for temporary marking of hazards, seasonal buoy placements (e.g., ice-prone waters), or newly discovered dangers. They appear exclusively on electronic chart displays (ECDIS) or AIS-enabled navigational screens.
AIS AtoNs are clearly depicted on NOAA nautical charts using a magenta circle around the traditional AtoN symbol:
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Real/Synthetic AIS AtoNs: Shown with the label "AIS"
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Virtual AIS AtoNs: Shown with the label "V-AIS"
Understanding these symbols helps mariners quickly interpret AIS data and navigate with enhanced confidence and safety.
used in U.S. territories in the South Pacific, the square and triangle top marks shown on V-AIS aids are switched with each other.
The USCG Light List also identifies AIS aids. For example, for this safe water mark 
, the USCG light list entry provides information regarding the AIS message in the remarks column, as shown below.
ECDIS and NOAA paper nautical charts portrayal of the most common types of virtual AIS aids are shown in the table below.
*References from National Oceanic and Atmospheric Administration (NOAA) and United States Coast Guard (USCG)
