Definition
A surveillance technology in which an aircraft determines its own position using onboard navigation sources (typically GPS) and automatically broadcasts that position, along with altitude, velocity, identification, and other flight data, at regular intervals to ground stations and to other suitably equipped aircraft. Air traffic control and nearby aircraft receive these broadcasts to track traffic without relying on traditional radar interrogation.
Plain English
The aircraft works out where it is using GPS and continuously transmits that information so controllers and other aircraft know its exact position, altitude, and speed.
Context Anchor
You will see ADS-B discussed in avionics, instrument flying, traffic displays, and equipment requirements for certain controlled airspace.
Derivation
Each word describes part of how it works. Automatic — the aircraft sends the data on its own with no pilot or controller action. Dependent — the accuracy depends on the onboard navigation system (usually GPS). Surveillance — it is used to watch and track aircraft. Broadcast — the data is sent out openly, available to anyone with a receiver, rather than being a private reply to a radar interrogation.
Why Pilots Care
Provides real-time traffic awareness and enables more precise ATC separation, reducing the need for traditional radar coverage.
Analogy
ADS-B is like an aircraft continually sending a short status message: “This is who I am, this is where I am, and this is how I’m moving.” Other approved receivers can use that message to build a clearer traffic picture.
Intuition Check
“Automatic” does not mean the system can fly the aircraft or avoid traffic by itself. It means the aircraft’s equipment sends position reports automatically. “Dependent” does not mean unreliable; it means the system depends on the aircraft’s own position source instead of a ground radar measuring the aircraft’s location.
Example Sentence 1
Before flying into the Class B airspace, the pilot confirmed that the aircraft’s ADS-B Out equipment was operating correctly.
Example Sentence 2
ADS-B Out equipment is now required for flight in most controlled airspace above 10,000 feet.