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The Earth-centered, Earth-fixed coordinate system (acronym ECEF), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass.
The scale is true (k=1) on the equator so that multiplying its length on a printed map by the inverse of the RF (or principal scale) gives the actual circumference of the Earth. The bar scale on the map is also drawn at the true scale so that transferring a separation between two points on the equator to the bar scale will give the correct ...
In cartography, a conformal map projection is one in which every angle between two curves that cross each other on Earth (a sphere or an ellipsoid) is preserved in the image of the projection; that is, the projection is a conformal map in the mathematical sense. For example, if two roads cross each other at a 39° angle, their images on a map ...
Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).
The Digital Chart of the World (DCW) is a comprehensive digital map of Earth. It is the most comprehensive geographical information system (GIS) global database that is freely available as of 2006, although it has not been updated since 1992.
To show a location about Earth using the ECI system, Cartesian coordinates are used. The x–y plane coincides with the equatorial plane of Earth. The x-axis is permanently fixed in a direction relative to the celestial sphere, which does not rotate as Earth does. The z-axis lies at a 90° angle to the equatorial plane and extends through the ...
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The user can sight to the top of a tree using such a clinometer and read the angle to the top using a scale in the instrument. Topographic Abney levels are calibrated so when read at a distance of 66 feet (20 m) from the tree, the height to the tree above eye level can be directly read on the scale.