SK-42 ↔ WGS84 Coordinate Converter

Converting SK-42 coordinates to WGS84

SK-42 (the 1942 coordinate system, listed in EPSG as "Pulkovo 1942") is based on the Krassowsky ellipsoid and was for decades the main system of topographic maps in the USSR and several neighbouring countries. GPS receivers and web maps use WGS84, so the two systems are offset by roughly a hundred metres: about 117 m in Moscow and about 76 m in Novosibirsk. This tool converts in both directions and shows the result in the form you need: geodetic latitude and longitude, Gauss-Kruger grid coordinates or UTM.

What the tool does

• SK-42 → WGS84: input as B, L (decimal degrees or degrees, minutes, seconds) or as Gauss-Kruger X, Y. Output: WGS84 latitude and longitude, plus UTM with the zone chosen automatically.
• WGS84 → SK-42: input as latitude and longitude or UTM. Output: SK-42 B, L, the zone number and Gauss-Kruger X, Y with and without the zone prefix.
• Point list: paste lines such as "name X Y" or "X Y" and get a table, points on the map and a CSV file.

How to use it

1. Choose the direction and the format of your input coordinates.
2. For Gauss-Kruger, leave the zone on "Auto" when Y carries the zone prefix (7413187.97 means zone 7). If there is no prefix (413187.97), select the zone manually.
3. Enter a single point or paste a list and press Convert. Check the position on the map.

Gauss-Kruger zones here are 6° wide: the central meridian of zone N is 6N − 3 degrees, the false easting is N × 1 000 000 + 500 000 m and the scale on the central meridian is 1. This matches the EPSG:28404-28432 projections. In Russian practice X is the northing and Y the easting.

Parameters and accuracy

By default the tool follows the sequence given in GOST 32453-2017: first SK-42 → PZ-90.11 (ΔX = 23.557 m, ΔY = −140.844 m, ΔZ = −79.778 m, ωx = −0.00230″, ωy = −0.34646″, ωz = −0.79421″, m = −0.228·10⁻⁶), then PZ-90.11 → WGS84 (G1150) (ΔX = −0.013 m, ΔY = 0.106 m, ΔZ = 0.022 m, ωx = −0.00230″, ωy = 0.00354″, ωz = −0.00421″, m = −0.008·10⁻⁶). The transformation is applied to Earth-centred Cartesian coordinates with the Helmert formula as written in the standard. Heights are not converted: the calculation is made for a point on the ellipsoid surface, as in the two-dimensional EPSG transformations.

For comparison, two sets from the EPSG registry are available: EPSG:5044 (GOST R 51794-2008, stated accuracy 3 m) and EPSG:15865 (4.5 m). Across Russia, the GOST 32453-2017 set differs from EPSG:5044 by about 0.3-0.4 m, and EPSG:15865 differs from EPSG:5044 by 1.5 to 3 m. The accuracy of any of these options is limited by distortions in the SK-42 network itself and is a few metres. That is not enough for cadastral or engineering work.

MSK local systems are out of scope. The local coordinate systems of Russian regions have their own parameters (shift, rotation, scale, central meridian), which are distributed separately. This tool works only with SK-42 and WGS84.

Check against control points

Results were compared with the PROJ 9.3 library at seven points from Kaliningrad to Vladivostok. For EPSG:5044 and EPSG:15865 the EPSG operations themselves were used; for the GOST 32453-2017 set a chain of two Helmert transformations was built. The difference did not exceed 1 mm, and Gauss-Kruger coordinates matched EPSG:28404-28432 to the same level.

Data and method

Gauss-Kruger and UTM projections are computed with proj4js 2.9.0 (MIT licence); the Helmert transformation is implemented in this page's own code. Map basemaps: OpenStreetMap and Esri World Imagery. For background on coordinate systems, EPSG codes and UTM zones, see the guide coordinate systems, EPSG and UTM (in Turkish). Open-source libraries used and their licences: Data Sources.