The Automatic Identification System (AIS), originally designed to prevent ships at sea from colliding by allowing them to know the locations of nearby ships, is a technology for tracking maritime activity.
The data transmitted and received by AIS transponders has become increasingly valuable. Not just for the ships themselves but also for port authorities, coast guards, application developers, insurance companies and other businesses and organizations inside and outside the maritime industry .
AIS devices on ships send out information about that ship on a regular basis, generally speaking every few seconds. AIS transponders on nearby ships or on land then capture these signals.
This technology however has its limitations. AIS signals can’t reach beyond about 50 nautical miles. The AIS signals travel in a straight line while ships follow the curvature of the earth, meaning the ship’s AIS signal eventually drops out of range for the terrestrial receiver.
Satellite AIS greatly extends the range that signals attain compared to terrestrial AIS. Because satellites fly at high altitude over the earth, the signals transmitted and received by those AIS enabled satellites are not hindered by the earth’s curvature.
Satellite AIS allows for a more complete picture of the maritime activities in areas previously not covered by terrestrial AIS such as areas distant from ports and coastlines. Satellite AIS coverage makes for a more robust vessel tracking system.