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I'm attempting to reproject a coordinate in EPSG:3857 to EPSG:28992. The problem I'm running into is as follows:

When I use GeoPandas (ie. df.to_crs(epsg=28992)) to reproject my coordinates I get a value similar to this for my coordinate: (-587791.60, -5732776.63)

But when I go to the same coordinates (manually) in QGIS (with CRS set to 28992), and right click to get coordinates, the coordinates provided (in CRS 28992) are similar to this: (172839.93,442692.96)

How can I reproject in GeoPandas (or in any other Python library) to get (172839.93,442692.96) instead of (-587791.60, -5732776.63).

When converting a Polygon in GeoPandas and putting it into QGIS all measure of distance is lost (ie, a polygon that was a few km2, becomes a few mm2), but I'm not sure what I'm doing wrong. I've been googling for a few hours and I think it might have something to do with how the Datum is transformed, but I'm not sure what exactly that is nor how I can do it properly.

When I change the CRS to 28992 (I drag in OpenStreetMaps), I get the following prompt, which might have something to do with why the coordinates in QGIS are different from GeoPandas (again supporting my Datum transformation theory):enter image description here

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    Hi, Hard to know where the error is with the information provided. Please share the code, sample tables, and/or anything needed to reproduce the issue. Datum transformations can cause shifts, but usually very small ones. Generally half a meter, a few meters in some cases, more than 10 meters in very particular cases.
    – Gabriel De Luca
    May 13, 2022 at 1:45
  • Thanks for the feedback! I think I managed to solve the problem by converting from EPSG:4326 instead of 3857, since my understanding is that 4326 is a "flattened" version of 3857.
    – TimurO
    May 15, 2022 at 16:39
  • RDnew(-587791.60, -5732776.63) is near 0°E, 0°N, it looks like you have mixed up coordinates. Please add your own solution to your question as an answer for other Gisstack readers.
    – Hans Erren
    May 15, 2022 at 20:07

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I managed to solve the problem by converting from EPSG:4326 instead of from EPSG:3857.

My understanding is that EPSG:4326 is a "flattened/map" version of EPSG:3857, so they are equivalent.

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  • Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
    – Community Bot
    May 16, 2022 at 17:23
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    EPSG::4326 is a geographic 2D CRS while EPSG::3857 is a projected CRS that uses Mercator for the projection to a plane. Many GIS/map software display 4326 as a rectangle because they don't support showing it as an ellipsoid and/or to match other data.
    – mkennedy
    May 23, 2022 at 15:42

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