Out of the multitude of maritime geolocation and communication tools used by those at sea, the Automatic Identification System (AIS) has proved itself to be one of the most useful and hardy pieces of kit around.
AIS ships exchange data with one another and AIS base stations to make sure that the risk of a collision at sea remains minimal. AIS, whilst quite simple in its operation, provides a wealth of useful information for other seaborne vessels – such as unique identification for other ships, their position, course and speed.
The information gleaned from the AIS operations helps identify vessels alongside traditional marine radar – which to this day still remains a ship’s primary source of data for negotiating the waters.
AIS ships regularly broadcast information about their whereabouts and speed via their VHF (very high frequency) transmitters to AIS transponders fitted on other ships or on land-based systems, like vessel traffic services – the maritime equivalent of air traffic control.
Screens can display this information much like a radar can; allowing a team at sea, or on land, to accurately plot the details of other vessels.
AIS transponders on-board ships can emit signals horizontally to a distance of around 74Km (46 miles). Their range is much higher when broadcast vertically; although this doesn’t do much for nearby ships.
However, engineers and scientists behind the scenes at some of the world’s biggest space programmes are testing AIS VHF antennas in space, giving many hope that one day there will be a number of global satellite-based AIS-monitoring services.
AIS systems come in several different classes, A and B. The differences between which determine how much information can be displayed on an AIS receiver. Both use different kinds of transmission but are still classified as AIS standards all the same. Dual-channel receivers do exist, meaning that a base, or other ship can receive all available AIS-broadcasted information.