I recently played around with MarineTraffic and got interested in the tech behind it. Along with Vesseltracker, MarineTraffic is one of the leading and best-known providers of ship data based on AIS. It uses the Automatic Identification System (AIS) as a radio system for the exchange of navigation and other ship data.
AIS AIS refers to a radio system that improves the safety and guidance of vessel traffic by exchanging navigational and other vessel data.