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Geographic coordinate conversion has applications in cartography, surveying, navigation and geographic information systems. In geodesy, geographic coordinate conversion is defined as translation among different coordinate formats or map projections all referenced to the same geodetic datum. [1]
The reverse conversion is harder: given X-Y-Z can immediately get longitude, but no closed formula for latitude and height exists. See " Geodetic system ." Using Bowring's formula in 1976 Survey Review the first iteration gives latitude correct within 10 -11 degree as long as the point is within 10,000 meters above or 5,000 meters below the ...
The original WGS84 model had an absolute accuracy of 1–2 meters. WGS84 (G730) first incorporated GPS observations, taking the accuracy down to 10 cm/component rms. [14] All following revisions including WGS84 (G873) and WGS84 (G1150) also used GPS. [15] WGS 84 (G1762) is the sixth update to the WGS reference frame. [14]
The NAD83 map datum is sufficiently close to WGS84 for initial use. It is best to double check on a mapping site such as WikiMapia. It is best to double check on a mapping site such as WikiMapia. Cordinates obtained in China from commercial sources (Google, Bing, Baidu, etc.) may be obfuscated with GCJ-02 or BD-09 .
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).
Formulas for the Web Mercator are fundamentally the same as for the standard spherical Mercator, but before applying zoom, the "world coordinates" are adjusted such that the upper left corner is (0, 0) and the lower right corner is ( , ): [7] = ⌊ (+) ⌋ = ⌊ ( [ (+)]) ⌋ where is the longitude in radians and is geodetic latitude in radians.
A WKT format is defined to describe the operation methods and parameters used to convert or transform coordinates between two different coordinate reference systems. The WKT 1 and WKT 2 formats are incompatible regarding coordinate operations, because of differences in the modelling. [13]
The definition of NAD 83(1986) is based on the GRS 80 spheroid, as was WGS 84, so many older publications indicate no difference. WGS 84 subsequently changed to a slightly less flattened spheroid . This change in flattening is about 0.1 mm, a difference so small that computational programs often do not distinguish between the two ellipsoids. [ 13 ]