Abstract
This paper presents mathematical interdependences in converting geodetic coordinates into flat rectangular coordinates and inverse transformation recommended in the Ordinance by Prime Minister on the State System of Spatial References. It especially presents formulas contained in works by M. Hooijberg (1997) Practical Geodesy and R. Kadaj (2001) Projection Formulas and Parameters of Coordinate Systems. G-1.10. In order to illustrate uses of the presented formulas relevant calculation examples based on the reference ellipsoids WGS 84 and GRS 80 are included.