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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).
MSL – mean sea level [7] 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).
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.
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 ...
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 ...
Early world maps cover depictions of the world from the Iron Age to the Age of Discovery and the emergence of modern geography during the early modern period.Old maps provide information about places that were known in past times, as well as the philosophical and cultural basis of the map, which were often much different from modern cartography.
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The straight-line distance between the central point on the map to any other point is the same as the straight-line 3D distance through the globe between the two points. c. 150 BC: Stereographic: Azimuthal Conformal Hipparchos* Map is infinite in extent with outer hemisphere inflating severely, so it is often used as two hemispheres.