Definition
A surveillance system in which an aircraft automatically determines its own position using onboard navigation sources (typically GPS) and broadcasts that position, along with identification, altitude, velocity, and other data, on a defined radio frequency. Ground stations and other suitably equipped aircraft receive the broadcast and use it for traffic surveillance, separation, and situational awareness. ADS-B Out refers to the aircraft transmitting its data; ADS-B In refers to the aircraft receiving ADS-B and related services such as traffic and weather information.
Plain English
Each aircraft figures out where it is using GPS, then continuously broadcasts that information by radio. Ground controllers and nearby aircraft pick up the signal and can see exactly where everyone is.
Context Anchor
Seen in modern cockpit displays, traffic awareness systems, transponder discussions, and FIS-B weather and flight information services.
Derivation
The name describes how the system works. Automatic — it transmits on its own without pilot or controller action. Dependent — it depends on the aircraft's own navigation equipment to know its position, rather than being tracked from the ground like radar. Surveillance — it is used to monitor aircraft positions. Broadcast — the data is sent out openly to anyone in range, not directed to one receiver.
Why Pilots Care
It improves traffic awareness, supports more efficient routing, and is required equipment in much of the U.S. airspace for safety and regulatory compliance.
Grounding Statement
ADS-B is the aircraft and ground network sharing position and flight information automatically by broadcast signal.
Intuition Check
Do not read “dependent” as meaning unreliable or optional. In ADS-B, “dependent” means the system depends on the aircraft’s own position source to create the information it broadcasts.
Example Sentence 1
Before flying into Class B airspace, the pilot confirmed the aircraft was equipped with ADS-B Out and that it was transmitting correctly.
Example Sentence 2
ADS-B Out allows the aircraft to continuously broadcast its position while flying through Class A airspace.