Convert S-JTSK to WGS 84

Convert coordinates from S-JTSK (EPSG:4156) to WGS 84 (EPSG:4326) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.

From

Input (lon, lat (decimal degrees))

Output (lon, lat (decimal degrees))

Direct link to this transformation: epsgtransform.com/transform/epsg-4156-to-epsg-4326

About converting S-JTSK to WGS 84

S-JTSK (EPSG:4156) is the datum of the Czech and Slovak cadastre, defined on the Bessel 1841 ellipsoid. It is almost always met through the Křovák projection (EPSG:5514), a uniquely oblique conic designed in 1922 to cover both countries in a single low-distortion system.

EPSG publishes a handful of S-JTSK to WGS 84 transformations, the best at about ±1 m, fitted separately for the Czech Republic and Slovakia. For cadastral-grade work both countries provide grid-based corrections in their national tooling.

Watch the axis convention: classic Křovák coordinates are southing/westing (both positive toward the south-west), which trips up nearly every GIS import at least once.

Why people convert EPSG:4156 to EPSG:4326

Publishing Czech or Slovak cadastral data on web maps
Integrating S-JTSK municipal GIS layers with GPS data
Georeferencing historical maps of Czechoslovakia
Converting Křovák coordinates for cross-border projects

Try it: Prague, Czechia

Input (EPSG:4156): 14.4378, 50.0755

Official EPSG transformations from S-JTSK to WGS 84

The EPSG Geodetic Parameter Dataset defines 4 transformations between S-JTSK (EPSG:4156) and WGS 84 (EPSG:4326). Each applies to a specific area — pick the one whose area of use covers your data.

S-JTSK to WGS 84 (1)

EPSG:1623±1 mBest accuracy

Method:: Position Vector transformation (geog2D domain)
Area of use:: Czechia
Scope:: (null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences.

Parameter	Value	Unit
X-axis translation(tx)	570.8	metre
Y-axis translation(ty)	85.7	metre
Z-axis translation(tz)	462.8	metre
X-axis rotation(rx)	4.998	arc-second
Y-axis rotation(ry)	1.587	arc-second
Z-axis rotation(rz)	5.261	arc-second
Scale difference(ds)	3.56	parts per million

Parameter values from S-JTSK to ETRS89 (1) (code 1622). Assumes ETRS89 and WGS 84 can be considered the same to within the accuracy of the transformation. Replaced by S-JTSK to WGS 84 (5) (code 5239).

S-JTSK to WGS 84 (4)

EPSG:4836±1 m

Method:: Position Vector transformation (geog2D domain)
Area of use:: Slovakia
Scope:: (null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences.

Parameter	Value	Unit
X-axis translation(tx)	485	metre
Y-axis translation(ty)	169.5	metre
Z-axis translation(tz)	483.8	metre
X-axis rotation(rx)	7.786	arc-second
Y-axis rotation(ry)	4.398	arc-second
Z-axis rotation(rz)	4.103	arc-second
Scale difference(ds)	0	parts per million

Parameter values from S-JTSK to ETRS89 (4) (code 4827). Assumes ETRS89 and WGS 84 can be considered the same to within the accuracy of the transformation.

S-JTSK to WGS 84 (5)

EPSG:5239±1 m

Method:: Coordinate Frame rotation (geog2D domain)
Area of use:: Czechia
Scope:: (null/copy) Approximation for medium and low accuracy applications assuming equality between plate-fixed static and earth-fixed dynamic CRSs, ignoring static/dynamic CRS differences.

Parameter	Value	Unit
X-axis translation(tx)	572.213	metre
Y-axis translation(ty)	85.334	metre
Z-axis translation(tz)	461.94	metre
X-axis rotation(rx)	-4.9732	arc-second
Y-axis rotation(ry)	-1.529	arc-second
Z-axis rotation(rz)	-5.2484	arc-second
Scale difference(ds)	3.5378	parts per million

Parameter values from S-JTSK/05 to WGS 84 (1) (code 5227). Assumes ETRS89 and WGS 84 can be considered the same to within the accuracy of the transformation. Replaces tfm code 1622.

S-JTSK to WGS 84 (3)

EPSG:15965±6 m

Method:: Geocentric translations (geog2D domain)
Area of use:: Europe - Czechoslovakia
Scope:: Military survey.

Parameter	Value	Unit
X-axis translation(tx)	589	metre
Y-axis translation(ty)	76	metre
Z-axis translation(tz)	480	metre

Derived at 6 stations.

Convert EPSG:4156 to EPSG:4326 in code

The same transformation with common GIS tools and libraries:

from pyproj import Transformer

transformer = Transformer.from_crs("EPSG:4156", "EPSG:4326", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)

Source: EPSG:4156 — S-JTSK

geographic system using latitude and longitude on an ellipsoid · Area of use: Europe - Czechoslovakia

+proj=longlat +ellps=bessel +towgs84=589,76,480,0,0,0,0 +no_defs +type=crs

More about EPSG:4156 →

Target: EPSG:4326 — WGS 84

geographic system using latitude and longitude on an ellipsoid · Area of use: World (by country)

+proj=longlat +datum=WGS84 +no_defs +type=crs

More about EPSG:4326 →

Frequently asked questions

Why do my Křovák coordinates appear mirrored or in the wrong hemisphere?: Classic S-JTSK / Křovák uses positive-south, positive-west axes. Use the East-North variant consistently, or negate the axes before transforming.
How accurate is S-JTSK to WGS 84?: The published Helmert fits are good to about 1 m. Czech and Slovak authorities provide grid corrections for centimetre-level cadastral work.
How accurate is converting S-JTSK to WGS 84?: The most accurate official EPSG transformation between these systems is accurate to about ±1 m within its stated area of use. Browser-based converters approximate datum shifts with Helmert parameters; for surveying-grade work apply the official transformation in a desktop GIS.
Does my data leave the browser when I use this converter?: No. All coordinate transformations are computed locally in your browser using proj4js. The coordinates you enter are never transmitted to any server.

Need the reverse? Convert EPSG:4326 to EPSG:4156 →