As of 2015, there are several real-time ship trackers online, including Marine Traffic and Vessel Finder. These sites use information transmitted by a ship's Automatic Identification System (AIS) transponder to display its name, location, speed, course and other details.
Marine Traffic covers coastal areas that have a land-based AIS receiver installed. A ship's location is displayed on a map in real-time, but locations may not be updated if the ship travels out of range. The range for AIS technology is approximately 30 to 50 nautical miles from shore.
Vessel Finder typically updates a vessel's location on its map every 60 seconds. Visitors to the site can search for a specific ship by name to view its location.