The contour lines were derived from the Digital Terrain Model of the Czech Republic, 5th Generation (DMR 5G). The basic interval is 1 m, with an attribute distinguishing index contour lines at an interval of 5 m. In flat terrain, supplementary contour lines at an interval of 0.5 m are added. Given the requirements for universal use in 3D visualisation across a wide range of GIS and CAD software, the contour line objects in this dataset are represented by a three-dimensional vector spatial component with coordinates X, Y, H. The altitude H in the Baltic Vertical Datum – After Adjustment (Bpv) is also stored as the attribute "HEIGHT", providing additional options for labelling contour lines when creating maps. The dataset further contains a supplementary layer of form lines, represented by a two-dimensional vector spatial component with coordinates X, Y. Contour lines are not intended for terrain analyses (e.g., visibility, slope, aspect); for these purposes, it is recommended to use the DMR 4G or DMR 5G products.