Definition
A surveillance technology in which an aircraft determines its own position using satellite navigation (GPS) and automatically broadcasts that position, along with altitude, velocity, and identification data, to ground stations and to other suitably equipped aircraft. Air traffic control and nearby aircraft receive these broadcasts in near real time, allowing them to track the aircraft without the use of conventional radar.
Plain English
The aircraft figures out where it is using GPS and constantly transmits that information out for everyone to hear—controllers on the ground and other aircraft nearby. It replaces or supplements radar with a steady stream of self-reported position data.
Context Anchor
You will encounter this term in equipment requirements, airspace rules, traffic displays, and discussions of how air traffic control tracks aircraft.
Derivation
Each word describes one part of how the system works. Automatic—it transmits on its own without the pilot or controller asking. Dependent—the data depends on the aircraft's own onboard navigation (mainly GPS), not an outside radar bouncing signals off it. Surveillance—it is used to watch and track aircraft. Broadcast—the information is sent out openly for any receiver in range to pick up.
Why Pilots Care
It provides real-time traffic information, supports more direct routing, reduces controller workload, and is required equipment for flight in most controlled airspace.
Intuition Check
Automatic does not mean the airplane flies itself. Dependent does not mean optional; it means the system depends on information produced by the aircraft’s own equipment.
Example Sentence 1
Before flying into the Class B airspace, the pilot confirmed the aircraft's ADS-B Out equipment was transmitting correctly.
Example Sentence 2
Because the aircraft was equipped with Automatic Dependent Surveillance-Broadcast, the controller could provide precise traffic advisories without radar coverage.