The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vertical datum). The term elevation is mainly used when referring to points on the Earth's surface, while altitude or geopotential height is used for points above the surface, such as an aircraft in flight or a spacecraft in orbit, and depth is used for points below the surface.
Elevation is not to be confused with the distance from the center of the Earth. Due to the equatorial bulge, the summits of Mount Everest and Chimborazo have, respectively, the largest elevation and the largest geocentric distance.
Video Elevation
Maps and GIS
GIS or geographic information system is a computer system that allows for visualizing, manipulating, capturing, and storage of data with associated attributes. GIS offers better understanding of patterns and relationships of the landscape at different scales. Tools inside the GIS allow for manipulation of data for spatial analysis or cartography.
A topographical map is the main type of map used to depict elevation, often through use of contour lines. In a Geographic Information System (GIS), digital elevation models (DEM) are commonly used to represent the surface (topography) of a place, through a raster (grid) dataset of elevations. Digital terrain models are another way to represent terrain in GIS.
USGS (United States Geologic Survey) is developing a 3D Elevation Program (3DEP) to keep up with growing needs for high quality topographic data. 3DEP is a collection of enhanced elevation data in the form of high quality LiDAR data over the conterminous United States, Hawaii, and the U.S. territories. There are three bare earth DEM layers in 3DEP which are nationally seamless at the resolution of 1/3, 1, and 2 arcseconds.
Maps Elevation
Global 1-kilometer map
This map is derived from GTOPO30 data that describes the elevation of Earth's terrain at intervals of 30 arcseconds (approximately 1 km). It uses color and shading instead of contour lines to indicate elevation.
Hypsography
Hypsography is the study of the distribution of elevations on the surface of the Earth, although the term is sometimes also applied to other rocky planets such as Mars or Venus. The term originates from the Greek word ???? "hypsos" meaning height. Most often it is used only in reference to elevation of land but a complete description of Earth's solid surface requires a description of the seafloor as well. Related to the term hypsometry, the measurement of these elevations of a planet's solid surface are taken relative to mean datum, except for Earth which is taken relative to the sea level.
Temperature
In the troposphere, temperatures decrease with altitude. This lapse rate is approximately 6.5 °C/km.
See also
- Height
- Orthometric height
- Geodesy
- Geodesy of North America
- Sea Level Datum of 1929 later National Geodetic Vertical Datum of 1929 (NGVD 29)
- North American Vertical Datum of 1988 (NAVD 88)
- Geodesy of North America
- List of European cities by elevation
- List of highest mountains
- List of highest towns by country
- Normaal Amsterdams Peil
- Normalhöhennull
- Physical geography
- Table of the highest major summits of North America
- Topographic isolation
- Topographic prominence
- Topography
- Vertical pressure variation
References
External links
- U.S. National Geodetic Survey website
- Geodetic Glossary @ NGS
- NGVD 29 to NAVD 88 online elevation converter @ NGS
- United States Geological Survey website
- Geographical Survey Institute
- Downloadable ETOPO2 Raw Data Database (2 minute grid)
- Downloadable ETOPO5 Raw Data Database (5 minute grid)
- Find the elevation of any place
Source of the article : Wikipedia
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