Aids To Navigation

How is AIS used on aids to navigation?

AIS transmitters can also be affixed to a floating or fixed aid to navigation (ATON), such as a buoy, beacon, or light. The AIS broadcast provides the position and purpose of an aid, such as a port or starboard lateral buoy, even before it is close enough to be visible from a ship or to provide a radar return. This can help mariners confirm their ship's position or to prepare to make a turn that is based on passing a particular aid.

Three types AIS ATONs

There are thousands of buoys and beacons in U.S. waters. A growing number of these are AIS ATONs, of which there are three types. The Coast Guard calls these “real” (or “physical”), “synthetic,” and “virtual.”
  • Real AIS ATON - A physical aid to navigation structure on which an AIS transmitter is affixed and from which AIS messages are broadcast.
  • Synthetic AIS ATON - A physical aid to navigation structure, without an AIS transmitter, but for which AIS messages are broadcast from another (usually land-based) location.
  • Virtual AIS ATON - An aid to navigation with no physical structure. It exists only through AIS messages broadcast from another location. A few uses of virtual ATONs include environments where buoys are moved seasonally, such as in sea ice, or where a marker needs to be placed quickly, such as to mark a newly identified isolated danger or wreck. These aids can only be seen on an Electronic Chart Display and Information System (ECDIS), or other AIS enabled display, such as a ship’s radar.

AIS ATONs on NOAA nautical charts are portrayed with a magenta circle, enclosing an ATON symbol. The same symbol is used to depict both real and synthetic AIS ATONs, with a magenta “AIS” label next to the circle. Virtual AIS ATONs have a “V-AIS” label. The table below shows examples of how non-AIS and AIS ATONs are shown on NOAA nautical charts.