Definition
A surveillance technology in which an aircraft determines its own position using satellite navigation and automatically broadcasts that position, along with identity, altitude, velocity, and other data, at regular intervals. Ground stations and other suitably equipped aircraft receive these broadcasts directly, providing real-time traffic and surveillance information without the need for radar interrogation.
Plain English
The aircraft works out where it is using GPS and constantly tells everyone — air traffic control and nearby aircraft — its position, altitude, and speed. It does this on its own, automatically, several times a second.
Context Anchor
You will see ADS-B in traffic displays, aircraft equipment requirements, transponder discussions, and airspace rules that require position reporting equipment.
Derivation
The name describes how it works. 'Automatic' — it transmits on its own, with no pilot action. 'Dependent' — it depends on the aircraft's own navigation system (usually GPS) to know where it is. 'Surveillance' — it serves the same purpose as radar, letting controllers see traffic. 'Broadcast' — it sends the information out to anyone listening, rather than replying only when asked.
Why Pilots Care
It provides real-time traffic awareness, supports safer separation, and enables operations in areas without radar coverage.
Analogy
Like phones sharing location with each other through an app, except the information helps aircraft avoid conflicts and fly more direct routes.
Intuition Check
Do not read dependent as meaning weak or optional. Here, dependent means the report is based on the aircraft's own position source, rather than being measured entirely from the ground.
Example Sentence 1
Before departing into Class B airspace, the pilot confirmed the ADS-B Out transponder was transmitting correctly.
Example Sentence 2
ADS-B Out equipment allows the aircraft to be tracked continuously even outside radar range.