AGL
Above Ground Level
Last updated: April 20, 2026 · Maintained by Aviatr Editorial Team
What is AGL?
AGL (Above Ground Level) measures altitude from the terrain directly beneath the aircraft, not from sea level. VFR minimum heights over congested and open terrain, airspace floors near airports, and circuit-pattern altitudes are all expressed in feet AGL, making it the primary reference for low-altitude flight safety.
How is AGL used?
AGL matters most during low-altitude VFR operations. Circuit altitude at an uncontrolled airfield is typically 1,000 feet AGL; the minimum safe height over a congested area in EASA airspace is 1,000 feet AGL; over open countryside the minimum drops to 500 feet AGL under SERA. Since the altimeter reads MSL, pilots compute AGL by subtracting the aerodrome elevation from the indicated altitude — an aircraft at 3,500 feet MSL over terrain at 1,500 feet MSL is 2,000 feet AGL. This conversion is routine during approach briefings and traffic-pattern entry. IFR departure procedures publish obstacle clearance altitudes in both MSL (for the altimeter) and AGL (for situational awareness). Radio altimeters on larger aircraft report AGL directly, providing an independent check during approach to landing that is especially valuable in low-visibility Category II and III operations.