ShipPlotter displays complete information about ships that are within VHF range of your position using the Universal Automatic Identification System (AIS).
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) and 162.025 (ch 88) 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.
ShipPlotter decodes the AIS digital signals from each ship using the sound card in your PC. You need a suitable VHF band radio receiver tuned to one of the two AIS channels. The program decodes the received digital data and displays it in a variety of formats.