Definition
The use of radar to monitor the position and movement of aircraft within a defined area of airspace, allowing controllers to observe traffic, provide separation, and issue advisories based on what is displayed on the radar scope.
Plain English
Air traffic controllers watching aircraft on radar so they can keep track of where each one is and what it's doing.
Context Anchor
You’ll see this term in descriptions of air traffic control services, especially around busy airports and controlled airspace where controllers use radar displays.
Derivation
Radar comes from 'Radio Detection and Ranging.' Surveillance comes from the French 'sur' (over) and 'veiller' (to watch) -- literally 'to watch over.' Together: watching over aircraft using radio detection.
Why Pilots Care
It enables controllers to maintain safe separation between aircraft and provide traffic advisories.
Intuition Check
“Surveillance” does not mean secret monitoring, and it does not mean the controller is flying the airplane. In this context, it means air traffic control is observing aircraft positions on radar to support safe traffic management.
Example Sentence 1
Once clear of the mountains, the controller advised the pilot they were now under radar surveillance and could expect traffic advisories.
Example Sentence 2
Radar surveillance allows the facility to provide traffic information to pilots operating under visual flight rules.