EPSG

EPSG guidance note #7-2, http://www.epsg.org

2021-09-08

See methods 1031 and 1035 for similar tfms operating between other CRSs types.

Note: These formulas have been transcribed from EPSG Guidance Note #7-2. Users are encouraged to use that document rather than the text which follows as reference because limitations in the transcription will be avoided. Transformation of coordinates from one geographic coordinate reference system into another is often carried out as a concatenation of the following operations: (geographical to geocentric) + (geocentric to geocentric) + (geocentric to geographic) The Coordinate Frame Rotation (geog2D domain) transformation has 5 steps: (i) geographic 2D coordinates are converted to 3D using EPSG coordinate operation method code 9659; (ii) geographic 3D coordinates are converted to geocentric coordinates using EPSG coordinate operation method code 9602; (iii) the middle step of the concatenated transformation, from geocentric coordinates to geocentric coordinates, uses the Geocentric translations(geocentric domain) method, EPSG method code 1031; (iv) the geocentric coordinates are converted to geographic 3D using EPSG coordinate operation method code 9602; (v) finally the geographic 3D coordinates are converted to geographic 2D using EPSG coordinate operation method code 9659.

(For the geocentric step only). Given a three parameter datum shift from WGS 84 to ED50 for this North Sea area is given as dX = +84.87m, dY = +96.49m, dZ = +116.95m. The WGS84 geographical coordinates convert to the following WGS 84 geocentric values using the above formulas for X, Y, Z: XA = 3771 793.97m YA = 140 253.34m ZA = 5124 304.35m Applying the given datum shifts to these, we obtain new geocentric values now related to ED50: XB = 3771 878.84m YB = 140 349.83m ZB = 5124 421.30m