The tracking of ships on this D!V Live Ship Movements web site is accomplished using information broadcast from each ship as a part of the Automatic Identification System (AIS). Each ship equipped with the necessary AIS radio transponder, transmits their identification, position, speed and heading, and other information on a regular basis. Other ships can receive this information and using on-board display systems, watch the movement of all AIS equipped ships in the area, much like on radar.
These same broadcasts are received at the Boca Raton AIS Receiving Station and plotted using specialized computer programs. The resulting ship plots are then transferred to this web site for general viewing.
AIS is a VHF radio signal in the maritime band. Much like broadcast television, it is limited to line-of-site reception. As a result, ships will be seen appearing and disappearing from this web site display, as they move closer, farther away, or pass behind obstructions such as high rises in the port vacinity.
Atmospheric conditions can also affect the range at which ship signals can be received. At times ships seen on this D!V Live Ship Movements web site will include those in the Port of Miami area and the Port of Palm Beach. Most often Port Everglades and the coast to the north and beyond the location of the Boca Raton receiving site will be best covered.
A comprehensive description of the Automatic Identification System can be found at this U.S. Coast Guard web site:
The navigation information broadcast by AIS is obtained automatically from on-board ship systems. Some of the other information broadcast must be entered by the ship's crew and is not always updated or accurate.
