AIS Transponder/Receiver: now mandatory on all large commercial and passenger ships, the Universal Automatic Identification System uses VHF radio signals to transmit ship's information to all AIS enabled radio receivers in range (typically 20-40 miles). SOB "reads" this data and graphically displays the acquired targets directly on the chart screen. The received information includes: latitude/longitude, course, speed, ship size and type, destination and eta. Navigation aids are also increasingly being fitted with AIS devices to transmit their precise location.
