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  2. Height above ground level - Wikipedia

    en.wikipedia.org/wiki/Height_above_ground_level

    In aviation, atmospheric sciences and broadcasting, a height above ground level (AGL [1] or HAGL) is a height measured with respect to the underlying ground surface.This is as opposed to height above mean sea level (AMSL or HAMSL), height above ellipsoid (HAE, as reported by a GPS receiver), or height above average terrain (AAT or HAAT, in broadcast engineering).

  3. Airspace class (United States) - Wikipedia

    en.wikipedia.org/wiki/Airspace_class_(United_States)

    A route with a 4-digit code contains no segment higher than 1,500 feet AGL, while a 3-digit code indicates that one or more segments of the route exist at altitudes higher than 1,500 feet AGL. [23] For example, the route VR1234 would indicate a VFR route exclusively below 1,500 feet AGL, while IR567 would indicate an IFR route with at least one ...

  4. List of Class C airports in the United States - Wikipedia

    en.wikipedia.org/wiki/List_of_Class_C_airports...

    The innermost ring with a radius of 5 nautical miles (9 km) typically extends from the surface area around the airport to 4,000 feet (1,220 m) AGL (above ground level; charted in MSL), and an outer ring, with a radius of 10 nautical miles (19 km) that typically surrounds the inner ring and extends from a floor at 1,200 feet (370 m) AGL, (also ...

  5. National Airspace System - Wikipedia

    en.wikipedia.org/wiki/National_Airspace_System

    Class B airspace extends from the surface up to 10,000 ft. AGL and is the area above and around the busiest airports (e.g., LAX, MIA, CVG) and is also heavily controlled. A side view of Class B airspace resembles an upside-down wedding cake with three layers becoming bigger toward the top.

  6. Airspace - Wikipedia

    en.wikipedia.org/wiki/Airspace

    Class A airspace is generally the airspace from 18,000 feet (~3.4 miles, 5.5 km) mean sea level (MSL) up to and including flight level (FL) 600 (~11.4 miles, 18.3 km), including the airspace overlying the waters within 12 nautical miles (NM) (~13.8 miles, 22.2 km) of the coast of the 48 contiguous states and Alaska. Unless otherwise authorized ...

  7. Airspace class - Wikipedia

    en.wikipedia.org/wiki/Airspace_class

    Class E airspace exists above Class G surface areas from 14,500 ft (4,400 m) MSL to 18,000 ft (5,500 m) MSL. Federal airways from 1,200 ft (370 m) AGL to 18,000 ft (5,500 m) MSL within 4 miles (6 km) of the centerline of the airway is designated Class E airspace. Airspace at any altitude over FL600 (60,000 ft; 18,300 m) (the ceiling of Class A ...

  8. Ordnance datum - Wikipedia

    en.wikipedia.org/wiki/Ordnance_datum

    An ordnance datum (OD) is a vertical datum used by an ordnance survey as the basis for deriving altitudes on maps. A spot height may be expressed as above ordnance datum (AOD). Usually mean sea level (MSL) at a particular place is used for the datum.

  9. United Air Lines Flight 553 - Wikipedia

    en.wikipedia.org/wiki/United_Air_Lines_Flight_553

    [1]: 7 Published procedures, and pilots operating under instrument flight rules, use mean sea level (MSL) as the point of reference for measuring altitude; at Midway Airport, an altitude of 1,040 feet (320 m) MSL corresponded to an actual height above ground level (AGL) of only 429 feet (131 m). [1]: 7 The aftermath of Flight 553