I'm having an issue transforming a point from EPSG:3844 to EPSG:3857 using Proj4JS. The transformation it performs seems off compared to the result given by PostGIS, pyproj, rgeo-proj4 or even epsg.io.

PostGIS sample:

select st_astext(st_transform(st_geomfromtext('point(432142.945 474552.670)', 3844), 3857));

This is the code in question (JSFiddle):

    '+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=2.329,-147.042,-92.08,0.309,-0.325,-0.497,5.69 +units=m +no_defs +type=crs',
    '+proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs +type=crs',
const actual = proj4('EPSG:3844', 'EPSG:3857', [432142.945, 474552.67]);
const expected = [2685681.568887065, 5743146.959786006];
console.log('Actual:', actual);
console.log('Expected:', expected);
<script src="https://cdnjs.cloudflare.com/ajax/libs/proj4js/2.8.0/proj4.js"></script>

I suspect it has something to do with the Helmert transformation parameters given in +towgs84=2.329,-147.042,-92.08,0.309,-0.325,-0.497,5.69? If so, what are the correct parameters?

1 Answer 1


You are right regarding wrong towgs84 parameters. If you take the ones from https://spatialreference.org/ref/epsg/3844/html/:


you'll get much better result: [2685681.014671648, 5743147.970431625]. It's still not exactly what you expect, but at least you know where the discrepancy comes from.

  • Is there a central authority for this? I've also seen a different set of parameters in this commit that offers a result that's closer to the expected value. Although at this point I'm questioning everything - what's the correct value? It's just an assumption that the expected value I mentioned is right.
    – mrk
    Jan 3 at 8:59
  • Official place for EPSG:3844 is epsg.org/crs_3844/Pulkovo-1942-58-Stereo70.html, but unfortunately WKT info there epsg.org/crs/wkt/id/3844 now gives data in WKT2 format, which does not have info about towgs84 transform.
    – TomazicM
    Jan 3 at 9:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.