Definition
The function performed by air traffic control to track aircraft positions using radar, ADS-B, or other approved surveillance systems, allowing controllers to monitor traffic, provide separation, issue traffic advisories, and offer navigational assistance.
Plain English
It is how air traffic control sees where aircraft are. Using radar and similar systems, controllers watch each aircraft's position so they can keep them safely apart and help them get where they are going.
Context Anchor
Seen in risk management, traffic advisory, flight following, and instrument flight discussions where a pilot may receive help from air traffic control.
Derivation
Surveillance comes from the French sur- (over) and veiller (to watch), meaning 'to watch over.' In ATC, that is exactly what it describes: controllers watching over aircraft from the ground using electronic systems.
Why Pilots Care
It allows controllers to issue timely instructions, prevent conflicts, and provide traffic information that directly affects flight safety in controlled airspace.
Intuition Check
Do not assume ATC surveillance means ATC is guaranteeing that nothing can hit you. It means controllers may be able to see you and provide services, but the amount of help depends on the airspace, equipment, workload, and type of flight.
Example Sentence 1
Once clear of the mountains, the controller advised that ATC surveillance was reestablished and resumed flight following.
Example Sentence 2
ATC surveillance showed two aircraft converging, prompting an immediate vector to maintain separation.