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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]
Coordinate conversion is composed of a number of different types of conversion: format change of geographic coordinates, conversion of coordinate systems, or transformation to different geodetic datums. Geographic coordinate conversion has applications in cartography, surveying, navigation and geographic information systems.
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. Cordinates obtained in China from commercial sources (Google, Bing, Baidu, etc.) may be obfuscated with GCJ-02 or BD-09. Vector sources are more frequently affected than satellite sources.
Using it, it becomes possible to convert regional surveying points into the WGS84 locations used by GPS. For example, starting with the Gauss–Krüger coordinate, x and y, plus the height, h, are converted into 3D values in steps: Undo the map projection: calculation of the ellipsoidal latitude, longitude and height (W, L, H)
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]
NAD 83: North American Datum 1983: WGS 84: World Geodetic System 1984: NAVD 88: N. American Vertical Datum 1988: ETRS89: European Terrestrial Ref. Sys. 1989: GCJ-02: Chinese obfuscated datum 2002: Geo URI: Internet link to a point 2010
The WGS 84 datum surface is an oblate spheroid with equatorial radius a = 6 378 137 m at the equator and flattening f = 1 ⁄ 298.257 223 563. The refined value of the WGS 84 gravitational constant (mass of Earth's atmosphere included) is GM = 3.986 004 418 × 10 14 m 3 /s 2. The angular velocity of the Earth is defined to be ω = 72.921 15 × ...
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).