ShipPlotter displays complete information about ships that are within VHF range of your position using the Universal Automatic Identification System (AIS).
AIS is a system that ships use to communicate their positions to each other as part of the global maritime safety system. From December 2004, all ships over 300 tons must carry an AIS system which broadcasts information about the ship to any suitably equipped receiver.AIS uses very short bursts of high speed data on two VHF channels in the marine band. The two frequencies used are 161.975 (Marine ch 87 AIS) and 162.025 (ch 88 AIS) MHz. Ships broadcast their identity, position, course, speed and destination so that other ships can take account of their movements. Using a low cost radio scanner tuned to one or other of these channels and ShipPlotter software running on your PC, you will be able to see a radar-like real-time map (below) of all the large ships manoeuvring in your area together with information about their destination, estimated time of arrival and even the dimensions of each vessel.