Normally, an AIS-Receiving station using an external antenna placed 15 metres above sea level, will receive AIS information from AIS-equipped vessels that sail within a range of 15-20 nautical miles around it. Base stations located at a higher altitude may extend the range up to 40-60 NM depending on factors such as: elevation, antenna type, obstacles around the antenna and weather conditions.
The most important factor for an efficient reception is the elevation of the base station antenna. The higher, the better. For example, the MarineTraffic Network Team managed to track vessels 200 NM away, with a small portable antenna placed on an island mountain on 700 metres altitude! The majority of our base stations fully cover a range of 40 miles and, periodically, may receive information about some more distant vessels!
The MarineTraffic terrestrial-based AIS network provides extensive, real-time coverage of vessels' positions at several thousands of ports and coastal shipping routes worldwide. Satellite AIS data comes as an ideal supplement, as it enables the monitoring of vessels' tracks well beyond coastal regions, including the oceans!