title: SK-42 reference system
text: # SK-42 reference system
  
  The SK-42 reference system also known as the Krasovsky 1940 ellipsoid, is a coordinate system established in the Soviet Union in 1942 as Systema koordinat (Russian: Система координат 1942 года), and provides parameters which are linked to the geocentric Cartesian coordinate system PZ-90. It was used in geodetic calculations, notably in military mapping and determining state borders. The coordinate system SK-42 served as a foundation for developing the SK-63 reference system which was created and used primarily for civilian and industrial development purposes.
  
  The Krasovsky 1940 ellipsoid uses a semi-major axis (equatorial radius) a of 6,378,245 m, and an inverse flattening 1/f of $298.3^{:220}$
  
  ## Citations and notes
  
  * 1 2 3 E.M. Mazurova; S.M. Kopeikin; A.P. Karpik (2017). "Development of a terrestrial reference frame in the Russian Federation". Studia Geophysica et Geodaetica. 61 (4): 616–638. Bibcode:2017StGG...61..616M. doi:10.1007/s11200-015-1106-4. S2CID 133884317.
  * ↑ Office, United States Naval Observatory Nautical Almanac; Office, Great Britain Nautical Almanac (2005). Explanatory Supplement to the Astronomical Almanac. University Science Books. ISBN 9781891389450.
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