Definition
A surveillance technology in which an aircraft automatically determines its own position using onboard navigation sources (typically GPS) and broadcasts that position, along with identity, altitude, velocity, and other data, over a digital datalink. The broadcast is received by air traffic control ground stations and by other suitably equipped aircraft, replacing or supplementing traditional radar surveillance.
Plain English
The aircraft figures out where it is using GPS, then continuously transmits that position and other flight information to controllers and nearby aircraft.
Context Anchor
Seen in instrument flying, aircraft equipment discussions, traffic displays, and airspace requirements where ADS-B Out may be required.
Derivation
The name describes how it works. Automatic: it transmits on its own without the pilot or controller asking. Dependent: it depends on the aircraft's own navigation system (usually GPS) to know where it is. Surveillance: it provides the position information used to track aircraft. Broadcast: the data is sent out to anyone equipped to receive it, not point-to-point.
Why Pilots Care
It improves traffic awareness, supports more direct routing, and is required equipment for operations in most controlled airspace.
Analogy
ADS-B is like an aircraft continually saying, “Here I am, this is my altitude, and this is where I’m going,” so the right receivers can display that information.
Intuition Check
Do not assume “dependent” means the aircraft depends on radar. In ADS-B, “dependent” means the broadcast depends on the aircraft’s own position information.
Example Sentence 1
Before flying into Class B airspace, the pilot confirmed the aircraft's ADS-B Out equipment was operating and transmitting correctly.
Example Sentence 2
ADS-B Out equipment is required before entering Class B airspace.