The Basic Topographic Map of the Czech Republic 1 : 25 000 in the plane coordinate system of the European Terrestrial Reference System 1989 in the Universal Transverse Mercator projection of meridian zones (ETRS89-TMzn), hereinafter referred to as BTM 25/ETRS89, is a fundamental state cartographic work. As of July 1, 2023, BTM 25/ETRS89 expands the series of state cartographic works with a variant of ZTM 25 in the plane coordinate system ETRS89-TMzn, providing an alternative to ZTM 25 in the national coordinate system S-JTSK. In terms of content, ZTM 25/ETRS89 does not differ from the primary ZTM 25/S-JTSK. ZTM 25/ETRS89 depicts the entire territory of the Czech Republic in a continuous layout of map sheets, with the territory of the Czech Republic represented on 803 map sheets.
The sectional lines of the layout (inner frames) of ZTM/ETRS89 map sheets are formed by images of meridians and parallels at intervals determined by the map scale. A ZTM 25/ETRS89 map sheet thus covers an area of 5´ × 10´ (latitude × longitude). The dimensions do not include ancillary elements displayed on the printed version of the map sheet (e.g., overlap strip and frame and non-frame data). The dimensions of the printed version of the map, including all frame and non-frame data, are 480 mm × 770 mm. TIFF raster tiles measure 411 mm × 522 mm and, in addition to the area of the corresponding map sheet, also cover the overlap strip to adjacent sheets.
ZTM 25/ETRS89 map sheets are labeled with an alphanumeric nomenclature derived from the designation of the International Map of the World 1 : 1 000 000 (for the Czech Republic NM-33 and NM-34), measuring 6 degrees of longitude and 4 degrees of latitude. Additional characters specify the position of the map sheet of a given scale within the smaller-scale map sheet from which it is derived. Map sheets are also supplemented with the name of the map sheet, usually corresponding to the largest settlement on the sheet. In the case of ZTM 5/ETRS89, ZTM 10/ETRS89, and ZTM 25/ETRS89, this corresponds to the name of the respective ZTM 50/ETRS89. If no settlement is present on the map sheet, another unique geographic name (peak, watercourse, land parcel) from the sheet is used. ZTM 25/ETRS89 map sheets are created by dividing a ZTM 50/ETRS89 sheet into 2 rows of 5 minutes latitude and 2 columns of 10 minutes longitude into 4 map sheets, labeled sequentially within the ZTM 50/ETRS89 sheet from the northwest sheet with letters a, b, c, d. An example of a map sheet designation is Žďár nad Sázavou NM-33-08-6-B-c.
ZTM 25/ETRS89 contains planimetric, altimetric, and descriptive data. The planimetric data includes settlements and individual structures, roads, water bodies, administrative and cadastral boundaries, protected area boundaries, vegetation, and land cover. The altimetric data covers the terrain relief, represented by contours with a basic interval of 5 meters, terrain steps, rock formations, ravines, landslides or debris, isolated rocks and boulders, groups and rows of stones, and surveyed points with specified elevation. The descriptive data consists of standardized geographic names, names of municipalities and their parts, object type designations, contour and surveyed point elevations, names of protected areas. The printed map sheets and data files with the map print base in PDF format also include the ETRS89-TMzn and S-JTSK kilometer grid and the ETRS89 geographic grid, map frame with frame data (e.g., directional information of selected roads, names of twin settlements, neighboring countries description, coordinates) and non-frame data (e.g., legend, imprint information, graphical, numerical, and slope scale, interpolation scale of the ETRS89 coordinate system grid, graphical representation of the map in the layout of map sheets, meridian convergence and magnetic declination, graphical representation of administrative and cadastral boundaries and protected area boundaries, etc.).
The map content is depicted only within the territory of the Czech Republic. For planimetric representation in ZTM 25/ETRS89, cartographic generalization methods are applied to ensure graphical clarity – censal and normative selection (omission of elements based on quantitative and qualitative parameters, or further reduction), geometric generalization (displacement, simplification of shapes), cartographic displacement, enlargement of small dimensions, and classification changes (grouping multiple element categories into one). For buildings, aggregation methods may be applied.
The processing of ZTM 25/ETRS89 data began in 2020, and full coverage of the Czech Republic was completed in May 2023. The map is produced by transforming ZTM 25/S-JTSK data, followed by data verification and supplementation of frame and non-frame information. Source data for ZTM 25/S-JTSK include the Basic Geographic Database of the Czech Republic (ZABAGED^®) and the Geographic Names Database of the Czech Republic Geonames.
The creation and updating of ZTM 25/ETRS89 is managed by the Czech Office for Surveying, Mapping and Cadastre, which publishes ZTM 25/ETRS89 data free of charge as open data in the form of map content data files including non-frame information corresponding to map sheets in PDF format (print PDF files) and georeferenced map content data files corresponding to map sheets in TIFF format (TIFF raster tiles).

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