The SK-42 reference system also known as the Krasovsky 1940

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

, 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 A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured in t ...

PZ-90 PZ-90 (short for ''Parametry Zemli 1990 goda'', in russian: Параметры Земли 1990 года) is a geodetic datum defined for use in the GLONASS GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная � ...

. 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 In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

(equatorial radius) of 6,378,245 m, and an inverse flattening of 298.3

Citations and notes

Geodesy Navigation Surveying Geographic coordinate systems Geography of the Soviet Union Science and technology in the Soviet Union {{geodesy-stub