Coordinate systems supported in the ČÚZK view and download services:

The coordinate reference systems supported in the ČÚZK view and download services are marked by the standardized names and numeric codes. We use names and codes taken from the EPSG dataset, which is an international registry of coordinate reference systems and the standard for the use of coordinate reference systems in GIS applications as well. Furthermore, we use some alternative codes that are not standardized within the EPSG, but are also used in GIS applications.

System of the Unified Trigonometrical Cadastral Network(S-JTSK):

S-JTSK is legal geodetic reference system on the territory of the Czech Republic according to Government Regulation No. 159/2023 Coll. as amended. The view and download services support coordinate reference systems represented by EPSG codes 5514 and 5221 with the mathematical orientation of the coordinate axes (the x-axis points to the east, the y-axis points to the north, both coordinates are negative on the territory of the Czech Republic).

Name according to EPSG	EPSG code	Alternative code	Note
S-JTSK / Krovak East North	5514	102067*	Uses Krovak projection with the mathematical orientation of the coordinate axes, defined from the Greenwich prime meridian
S-JTSK (Ferro) / Krovak East North	5221	102066*	Uses Krovak projection with the mathematical orientation of the coordinate axes, defined from the Ferro prime meridian

*) alternative EPSG codes were used before the introduction of codes 5514 a 5221 into the EPSG dataset.

European Terrestrial Reference System 1989 (ETRS89):

ETRS89 is a legal geodetic reference system in the Czech Republic according to Government Regulation No. 159/2023 Coll. as amended and a mandatory coordinate reference system in the EU according to the INSPIRE Directive. Apart from expressing ETRS89 in geographical coordinates, the Government Regulation and INSPIRE allow the use of planar coordinate systems of its cartographic projections. The use of these coordinate reference systems is defined in the topic Coordinate reference systems.

Name according to EPSG	EPSG code	INSPIRE designation	Note
ETRS89	4258	ETRS89-GRS80	projection using geographic coordinates (also geographic projection or geographic 2D) is used
ETRS89 / LCC Europe	3034	ETRS89-LCC	Lambert Conic Conformal projection is used
ETRS89 / LAEA Europe	3035	ETRS89-LAEA	Lambert Azimuthal Equal Area projection is used
ETRS89 / UTM zone 33N (N-E)	3045	ETRS89-TM33N	Universal Transverse Mercator projection (UTM) is used, central meridian 15°
ETRS89 / UTM zone 34N (N-E)	3046	ETRS89-TM34N	Universal Transverse Mercator projection (UTM) is used, central meridian 21°

World Geodetic System 1984 (WGS84):

WGS84 is a legal geodetic reference system on the territory of the Czech Republic according to Government Regulation No. 159/2023 Coll. as amended. The following coordinate reference systems are supported in view and download services:

Name according to EPSG	EPSG code	Alternative code	Note
WGS 84	4326		projection using geographic coordinates (also geographic projection or geographic 2D) is used
WGS 84 / UTM zone 33N	32633		Universal Transverse Mercator projection (UTM) is used, central meridian 15°
WGS 84 / UTM zone 34N	32634		Universal Transverse Mercator projection (UTM) is used, central meridian 21°
WGS 84 / Pseudo-Mercator	3857	900913	Pseudo-Mercator projection is used (Popular Visualisation CRS / Mercator)

Height reference systems:

The following height reference systems are further used in the data, services and applications of the ČÚZK Geoportal:
Baltic Vertical System - After Adjustment (Bpv):

Bpv is a legal geodetic reference system on the territory of the Czech Republic according to Government Regulation No. 159/2023 Coll., as amended.

Name according to EPSG	EPSG code	Alternative code	Note
Baltic 1957 height	8357	5705*	Uses Normal heights, defined by mean sea level of the Baltic Sea in Kronstadt

*) EPSG code 5705 (Baltic 1977 height) was used as an alternative before the introduction of code 8357 within the EPSG dataset.

European Height Reference System (EVRS):

EVRS is a legal geodetic reference system on the territory of the Czech Republic according to Government Regulation No. 159/2023 Coll. as amended, and a legal coordinate reference system in the EU according to the INSPIRE Directive. The use of this reference system is defined in the topic Coordinate reference systems.

Name according to EPSG	EPSG code	Alternative code	Note
EVRF2007 height	5621		Uses Normal heights, defined by mean sea level of the North Sea in Amsterdam

Coordinate systems used for exporting raster and vector data files:

In addition to publishing data via the view and download services of the direct access, pre-packed raster and vector data files are published. These pre-packed files are provided within the relevant output units in the following coordinate reference systems:

Name	EPSG code
S-JTSK / Krovak East North	5514
WGS 84 (geographic 2D)	4326
WGS 84 / UTM zone 33N	32633
WGS 84 / UTM zone 34N	32634
ETRS89 (geographic 2D)	4258
ETRS89 / TM33	3045
ETRS89 / TM34	3046

Pre-packed files are provided in one or more of the above listed coordinate reference systems. The coordinate reference systems used for each data are specified in the metadata and on the information web pages of the relevant data.

Accuracy of transformations between coordinate systems:

Within the view and download services, approximate coordinate transformations are performed, which is given by the possibilities of the publishing software. The accuracy of the transformation between the S-JTSK and ETRS89 is in the order of decimetres to 1 m. Therefore, the result of a query to the service is not affected by this inaccuracy only when requesting the service in the coordinate system in which the source data is stored. The orthophoto of the Czech Republic is stored in both systems due to the requirement for service accuracy in S-JTSK and ETRS89-TMzn.

The following transformations are registered in the EPSG database for use in GIS applications:

Name according to EPSG	EPSG code	Conversion surface	Note
S-JTSK to ETRS89 (1)	1622		Transformation between legally given systems S-JTSK and ETRS89, with an approximate accuracy of decimetres to 1m.
S-JTSK-05 to ETRS89 (1)	5226		Transformation between the reference systems, the working S-JTSK/05 and the legally given ETRS89, whose accuracy is in the order of centimetres.
ETRS89 to Baltic 1957 height (2)	10567	CR2005.GTX*	Height transformation between the ETRS89 (GRS80) and Bpv reference systems with an accuracy of centimetres.
ETRS89 to ETRS89 + Baltic 1957 height (2)	10568

*) Conversion surface is stored in the standardized grid format compatible with GIS applications, license Creative Commons CC BY 4.0

For accurate transformations (with a mean position error of approximately 4 cm when converting between S-JTSK and ETRS89), the Transformation Service of the ČÚZK Geoportal is available, using the calculation module of the ETJTZU 2019 software. The client of the service - the Coordinate Transformation application - is available on the ČÚZK Geoportal and allows the transformation of coordinates of individual points, text files with coordinate lists or files in GML format.

Overview of the different definitions of the S-JTSK and S-JTSK/05 coordinate systems:

S-JTSK

S-JTSK is defined in the plane of the Krovak projection (double conformal conic projection in general position). The X-axis points south, the Y-axis points west. The X-axis is the image of the prime meridian located 42°30' east of the Ferro zero meridian. The definition of S-JTSK corresponds to the coordinate reference system registered under EPSG code 2065: S-JTSK (Ferro) / Krovak. However, this coordinate reference system is not suitable for the use in GIS applications due to the non-standard orientation of the coordinate axes. Therefore, coordinate reference systems that preserve the mathematical orientation of the coordinate axes (x-axis east, y-axis north) are used:

System	Orientation X / Y	Prime meridian
		Greenwich		Ferro
		Code	Name	Code	Name
S-JTSK	south / west	5513	S-JTSK / Krovak	2065	S-JTSK (Ferro) / Krovak
	east / north	5514	S-JTSK / Krovak East North	5221	S-JTSK (Ferro) / Krovak East North

In GIS applications, the most commonly used coordinate reference system is represented by the EPSG code 5514 and eventually 5221.

S-JTSK/05

Unlike S-JTSK, the S-JTSK/05 coordinate system is not legally given in the Czech Republic. However, it is used as a working system that mediates the transformation between ETRS89 and S-JTSK. The S-JTSK/05 system is defined by the so-called modified Krovak projection. The X-axis points south, the Y-axis points west. The S-JTSK/05 system is defined in the EPSG dataset in different ways, which, as in the case of S-JTSK, depend on the choice of the zero meridian and the orientation of the coordinate axes:

System	Orientation X / Y	Prime meridian
		Greenwich		Ferro
		Code	Name	Code	Name
S-JTSK/05	south / west	5515	S-JTSK/05 / Modified Krovak	5224	S-JTSK/05 (Ferro) / Modified Krovak
	east / north	5516	S-JTSK/05 / Modified Krovak East North	5225	S-JTSK/05 (Ferro) / Modified Krovak East North

Pozn.: souřadnice Y,X v systému S-JTSK/05 se vůči souřadnicím Y,X v systému S-JTSK liší o hodnoty diferencí v řádu centimetrů až decimetrů, a dále jsou souřadnice S-JTSK/05 posunuty vůči souřadnicím S-JTSK o hodnotu 5000 km, aby nedošlo k záměně obou systémů.