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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).
Each rectangular area covering one degree of latitude and one degree of longitude is divided into four smaller areas called quadrangles (in accordance with the World Geographic Reference System, or GEOREF), each spanning half a degree of latitude and half a degree of longitude. Each quadrangle has its MEF printed in it in thousands and hundreds ...
UN maps are, in principle, open source material and you can use them in your work or for making your own map. UN requests however that you delete the UN name, logo and reference number upon any modification to the map. Content of your map will be your responsibility. You can state in your publication, if you wish, something like: based on UN ...
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.
DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values, i.e., a Digital Elevation Model.This standard was originally developed in the 1970s to support aircraft radar simulation and prediction.
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 ...
The charts are marked with World Geographic Reference System or GEOREF grids, and at the center of each grid square a number shows the elevation (MSL) of the highest obstacle within that grid (the maximum elevation figure or MEF). Thus a pilot is alerted of how high he must fly while traversing that grid to assure clearance of all possible ...
It allowed for a model with n=m=180 to be defined, providing a raster for every half degree (30', 30 minute) of latitude and longitude of the world. [4] NIMA also computed and made available 30′×30′ mean altimeter derived gravity anomalies from the GEOSAT Geodetic Mission. 15′×15′ is also available.