As reference surface common for the EOV projection and the HD-72 Datum the Geodetic Reference System recommended by the International Union of Geodesy and Geophysics in 1967 (the IUGG GRS 1967) has been selected. The altitude system is defined above the Baltic sea.
The Hungarian reference system has been defined using the Hungarian Astrogeodetic Network adjusted on Krassovskij ellipsoid and transformed onto the IUGG GRS 1967 ellipsoid. In this procedure the Hungarian Datum 1972 (HD-72) has been defined as being located and oriented relatively at terrestrial Geodetic Datum point Szőlőhegy. The azimuth from Szőlőhegy to Erdőhegy is fixed.
The EOV system (Egységes Országos Vetületi rendszer, Uniform National Projection system) is a conformal cylindrical projection in transversal position used uniformly for the Hungarian civilian base maps.
Any point of the earth surface in Hungary is represented on the map by the EOV plane coordinates. For this - after reductions to the direct surface measurements - the projecting procedure is performed in two steps: firstly, from the ellipsoid to the best fitting Gauss-sphere and, secondly, from this sphere to the plane of EOV.
The HD-72-equivalent three-dimensional rectangular coordinates (XYZ) of a point can be obtained from the HD-72 IUGG GRS 1967 ellipsoidal coordinates of the point, using the IUGG GRS 1967 ellipsoid parameters and by help of known formulas.
In general case and for international use the transformation from EOV (and the respective heights)
to any other projection system can be performed as it follows: