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Known issues: Coordinate conversion (errors for some conversions).
Details on datums and ellipsoids

Below you find all parameters used for conversions of coordinates. First the different ellipsoids used, with the length of their axes. Next the different map datums, with the area in which they can be used and the parameters necessary to convert coordinates using the Helmert transform.
The Helmert transformation, also called a seven-parameter transformation, is a transformation method within a three-dimensional space. It is frequently used in geodesy to produce distortion-free transformations from one datum to another. The coordinates of a reference system B are derived from reference system A by the following formula:

with X, Y and Z the Cartesian coordinates of system B and A, cx, cy and cz the three translation parameters, s the scale factor and rx, ry and rz the three rotation parameters.

Ellipsoids
 Name Code Semi-major axis (a) Semi-minor axis (b) Inverse flattening (1/f) Airy 1830 AA 6377563.396 6356256.9092373 299.3249646 Australian National AN 6378160 6356774.7191953 298.25 Bessel 1841 BR 6377397.155 6356078.9628182 299.1528128 Bessel 1841 (Namibia) BN 6377483.865 6356165.3829663 299.1528128 Bessel Modified BM 6377492.018 6356173.5087127 299.1528128 CGCS2000 SG 6378137 6356752.3141404 298.257222101 Clarke 1858 CA 6378235.6 6356560.1397606 294.2606768 Clarke 1866 CC 6378206.4 6356583.799999 294.9786982 Clarke 1880 CD 6378249.145 6356514.8695498 293.465 Clarke 1880 (IGN) CG 6378249.2 6356515 293.46602129363 Clarke 1880 (Benoit) CF 6378300.789 6356566.435 293.46631553898 Everest (Brunei, E. Malaysia (Sabah and Sarawak)) EB 6377298.556 6356097.5503009 300.8017 Everest 1830 EA 6377276.345 6356075.4131402 300.8017 Everest 1956 (India and Nepal) EC 6377301.243 6356100.2283681 300.8017 Everest (Pakistan) EF 6377309.613 6356108.5705425 300.8017 Everest 1948 (W. Malaysia and Singapore) EE 6377304.063 6356103.0389931 300.8017 Everest 1969 (W. Malaysia) ED 6377295.664 6356094.6679152 300.8017 Geodetic Reference System 1967 RE 6378160 6356774.5160907 298.247167427 Geodetic Reference System 1980 RF 6378137 6356752.3141404 298.257222101 Helmert 1906 HE 6378200 6356818.1696279 298.3 Hough 1960 HO 6378270 6356794.3434343 297 Indonesian 1974 ID 6378160 6356774.5040855 298.247 International 1924 IN 6378388 6356911.946128 297 Krassovsky 1940 KA 6378245 6356863.0187731 298.3 Modified Airy AM 6377340.189 6356034.4479385 299.3249646 Modified Fischer 1960 FA 6378155 6356773.3204827 298.3 PZ-90 SN 6378136 6356751.3617457 298.257839303 South American 1969 SA 6378160 6356774.7191953 298.25 WGS 1972 WD 6378135 6356750.5200161 298.26 WGS 1984 WE 6378137 6356752.3142452 298.257223563 War Office WO 6378300 6356751.6891892 296
Datums