The original purpose of AIS (Automatic Identification System) transmissions was to stop boats from colliding at sea. For this reason, AIS is a ship-to-ship communication with vessels having both transponders and receivers.
AIS receivers don't just need to be on vessels though and are also placed on satellites and along shorelines. We use three sources of AIS data in Starboard and for AIS data from March 2023 you can see which source points are coming from.
Using satellites to receive AIS transmissions provides a global view of AIS data. We use Spire's Real-Time AIS (previously ExactEarth) constellation of Low Earth Orbit (LEO) satellites. We have used this data source since 1 May 2020.
When the vessel is far from shore, satellites are the main source of AIS data. Messages are often published in “bursts”.
When vessels are near a coastline, shore-based receivers receive AIS transmissions. We currently use S&P Global Market Intelligence's AIS Antenna Network. We have used this data source since 12 March 2023. Prior to this, we used ExactEarth's terrestrial network.
When a vessel is near a shore-based receiver, terrestrial AIS provides comprehensive low latency coverage.
Vessel based AIS
Satellite-enabled AIS receivers are fitted on vessels that travel throughout the busiest shipping lanes in the world. We have used this data source for class A messages since 12 March 2023 and for both class A and class B messages since 18 May 2023.
When a vessel is in a highly congested area that could overwhelm satellite receivers with too many messages and when they are out of reach of terrestrial receivers, vessel based AIS provides low latency coverage.