The Automatic Identification System (AIS) can be an enormously powerful anti-collision tool. In effect, every vessel with AIS automatically transmits an automated message giving position, course, and speed, which can be picked up by anyone with suitable equipment and shown on a display or superimposed on a radar or chartplotter screen. Many AIS receivers include a mini-computer that uses this data to calculate new information, like the boat’s closest point of approach (CPA) and time to CPA.
Receive-only AIS is useful for recreational craft, but AIS B is even better. It could be called AIS Lite, because it’s a cut-down version of the AIS A that’s used in commercial shipping, transmitting details of your position, course, and speed and receiving that information from ships. It’s been slow to be accepted, and there are concerns that in popular areas, it could overload ships’ watchkeepers with info. But the counter-argument is that receive-only AIS is like riding a bike without lights: it relies on you being able to see and avoid everyone else. AIS B gives your “bike” lights: it makes you visible. —T.B.
This article originally appeared in the January 2010 issue of Power & Motoryacht magazine.