The terrestrial-AIS-based MarineTraffic system does not cover 100% of the world's seas, but only specific coastal areas where a land-based AIS receiver is installed. Wider areas are covered with the addition of Satellite-AIS.
All vessels which are equipped with an operational AIS transponder and sail within the reception range of an AIS receiving station, installed on the shore, are depicted on the MarineTraffic Live Map. If there is no fresh information on a vessel's recent position, for 24 hours, this vessel is removed from the Live Map until we receive a new position of her.
Possible reasons for a vessel's position not picked up and displayed on the Live Map are:
- The vessel is not equipped with an AIS transponder or the transponder is not operational or the transponder is not properly working
- The vessel sails in an area where no nearby AIS receiving station exists and Satellite-AIS is not enabled for your account.
- The transmission power of the vessel's AIS transponder is not enough in order for a land-based station to receive the signals. This depends on the type of the transponder, the type and the height of the antenna and the quality of the cabling
- Especially for vessels equipped with a Class-B AIS transponder, the transmission power of AIS signals is much lower than the power of a Class-A transponder and, therefore, the reception range is much more restricted. None of our AIS receivers is close enough to receive class B signals, although class A (and some more powerful class B) signals are received and displayed.
- The AIS transponder of the vessel is not configured to transmit the correct information (e.g. MMSI number, ship's name etc.)
If you do have Satellite-AIS coverage enabled for your account and still cannot see a vessel, this usually means one of the following:
- The vessel is sailing in a busy area (without coverage from our terrestrial receiver network) and the satellite fails to receive a clear signal.
- The vessel is sailing at the Poles, where our coverage is limited.
- The vessel is equipped with a Class-B receiver, which is more difficult to be picked up by the satellite.