AIS (Automatic Identification System)

AIS is a VHF-band transponder system standardized in ITU-R M.1371 that broadcasts a ship’s identity, position, course, speed, and voyage data on two dedicated channels (AIS 1 on 161.975 MHz and AIS 2 on 162.025 MHz) using self-organizing time-division multiple access. SOLAS V/19.2.4 mandates Class A AIS on all ships of 300 GT and above on international voyages, all cargo ships of 500 GT and above on domestic voyages, and all passenger ships. It supports collision avoidance, VTS reporting, and shore traffic monitoring, but Rule 7 cautions against treating its data as a substitute for radar.