Automatic Dependent Surveillance-Broadcast (also called ADS-B) is a system by which airplanes constantly broadcast their current location, speed, flight plan, size and type of craft, and other information. This information is received by other airplanes and flight controllers. The purpose of the system is to reduce the risk of collisions between airplanes, as well as to reduce congestion by allowing for more effective management of air traffic.
The ADS-B system was developed in the 1990s. It relies on data from the Global Positioning System.