How AIS Works

What is AIS?

AIS stands for Automatic Identification System, and was designed for safer navigation for all marine vessels. AIS is basically split into Class A, Class B, and receivers. Class A is a radio transceiver that is required on nearly all tugs and commercial ships. It's used by ships and Vessel Traffic to identify targets, similar to how radar transponders are used by Air Traffic Control to identify aircraft. By use of VHF frequencies, ships transmit their GPS location, name, true heading, MMSI (a unique number that identifies the ship for hailing), speed, rudder angle, and more information on a constant, automatic basis. It is the answer to "What is that ship doing?"

Class B is basically a less robust version, and is intended for the use of pleasure boats and other vessels not required to use Class A. It also transmits information, and has been approved in most jurisdictions (most recently in the US). One issue people have with this is that once you've installed the equipment, it is very likely that you will eventually be required by law to use it. One camp finds this very handy and acceptable, and the other sees it as another way for "Big Brother" to keep tabs on you. Realistically, it "puts you on the screen" of the vessels around you in a way no radar reflector can, and is highly advisable when sailing in congested waters, or when shorthanded.


Use this map to see LIVE exactly what AIS is and does!
NOTE: This map is updated every 120 seconds.

Use your cursor to move the map in any direction.
Click any box to enlarge that area, and click on icons to see vessel information.
(NOTE: Do not double click icons.)

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