Definition
A virtual three-dimensional boundary defined by GPS coordinates that an aircraft, typically an unmanned aircraft (drone), is programmed not to cross. The aircraft's flight control system uses real-time position data to detect proximity to the boundary and will either alert the operator, prevent further movement toward the boundary, or refuse to take off inside a restricted zone.
Plain English
An invisible electronic fence drawn on a map. The aircraft knows where the fence is and won't fly through it.
Context Anchor
Seen in drone operations, electronic flight planning, aircraft tracking systems, and some airspace awareness tools.
Derivation
Combination of 'geo-' (Greek geo, meaning earth or ground) and 'fence' (a physical barrier marking a boundary). The word captures the idea of a barrier that exists in geographic space rather than as a physical object.
Why Pilots Care
Prevents accidental flight into restricted airspace and supports compliance during drone or low-altitude operations.
Grounding Statement
Picture a line drawn on an electronic map; the aircraft does not see a wall, but the system knows when the aircraft reaches that line.
Intuition Check
A geofence is not a physical fence. It is a software boundary based on position, and it does not by itself make a flight legal or safe.
Example Sentence 1
The drone refused to take off because the operator was standing inside the geofence around the airport.
Example Sentence 2
During the pipeline inspection the aircraft stayed safely inside the geofence established for the mission.