The height of any geographic point is its distance along a plumb line from the reference level. The value of the height of a point is called its mark [1] .
There are absolute and relative heights [2] [1] :
- the absolute height (height above sea level) is calculated from the average sea level or ocean level (in particular, in the former USSR - from the level of the Baltic Sea );
- the relative height (elevation) is calculated from any conditional level adopted in this case as zero.
The definition of height difference is called leveling .
For objects in the air, the geopotential height sometimes used (measured from sea level, but slightly different from absolute) [3] [4] [5] ; see also altitude . Height in the usual sense (as opposed to geopotential, angular , etc.) is called geometric [6] .
Less commonly, height is measured relative to the center of the earth . Interestingly, due to the polar compression of the Earth, the identification of the highest mountain on the planet becomes ambiguous. The highest point of the Earth above sea level is the top of Everest , and the most distant point from the center of the Earth is the top of the Chimborazo volcano [7] .
Maps and geographic information systems
On topographic maps , terrain heights are usually shown using iso-gypsum (lines of equal height) and elevations of characteristic points of the terrain.
In geographic information systems (GIS), digital elevation models are used as rasterized sets. They can also be represented as a digital surface model (digital terrain model).
See also
- National elevation systems in geodesy
- Baltic system of heights
- Geodetic height
- Flight altitude
- Height of sea surface
- Rapper (geodesy)
Notes
- ↑ 1 2 Engineering geodesy: a textbook for universities / ed. D. Sh. Mikheleva. - 4th ed., Corr. - M .: "Academy", 2004. - p. 8–9. - 480 s. - ISBN 5-7695-1524-4 .
- ↑ Popov V.N., Chekalin S.I. Geodesy: A textbook for universities. - M .: “Mining book”, 2007. - p. 34–35. - 518 s. - ISBN 5-91003-028-6 .
- ↑ Kotlyakov VM, Komarova AI Elsevier's Dictionary of Geography . - Elsevier, 2006. - P. 292. - 1072 p. - ISBN 9780080488783 .
- ↑ Topography of the pressure method // Big Soviet Encyclopedia : [in 30 t.] / Ch. ed. A. M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
- ↑ Khromov S.P., Mamontova L.I. Geopotential height // Meteorological dictionary. - 3rd ed. - L .: “Gidrometeoizdat”, 1974. - p. 111. - 568 p.
- ↑ Khromov S.P., Mamontova L.I. Altitude // Meteorological dictionary. - 3rd ed. - L .: “Gidrometeoizdat”, 1974. - p. 101. - 568 p.
- ↑ National Oceanic and Atmospheric Administration US Department of Commerce. How is the center point measured? (eng.) oceanservice.noaa.gov. The appeal date is July 15, 2019.