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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).
For elevations or altitudes, often just the abbreviation MSL is used, e.g., Mount Everest (8849 m MSL), or the reference to sea level is omitted completely, e.g., Mount Everest (8849 m). [ 7 ] Methods of measurement
The orthometric height (symbol H) is the vertical distance along the plumb line from a point of interest to a reference surface known as the geoid, the vertical datum that approximates mean sea level.
Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as the reference datum. Pressure altitude divided by 100 feet (30 m) is the flight level, and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions ...
Global MSL refers to a spatial average over the entire ocean area, typically using large sets of tide gauges and/or satellite measurements. [ 7 ] One often measures the values of MSL with respect to the land; hence a change in relative MSL or ( relative sea level ) can result from a real change in sea level, or from a change in the height of ...
In Great Britain, OD for the Ordnance Survey is Ordnance Datum Newlyn (ODN), defined as the MSL as recorded by the Newlyn Tidal Observatory between 1915 and 1921. [1]Prior to 1921, OD was Ordnance Datum Liverpool (ODL) defined as MSL as recorded in the Victoria Dock, Liverpool, during a short period in 1844.
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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 ...