[Qgis-user] Pseudo Mercator(OSM) @ EPSG:4326 bug?

[b.j.kobben at utwente.nl]

Most likely the service you are using is only able to provide its maptiles in 3857 and does not respond to the QGIS request to provide them in 4326 (or responds, but incorrectly)...


--
Barend Köbben

On 05/03/2018, 09:39, "Qgis-user on behalf of Idan Miara" <qgis-user-bounces at lists.osgeo.org<mailto:qgis-user-bounces at lists.osgeo.org> on behalf of idan at miara.com<mailto:idan at miara.com>> wrote:

Hi,

I might have found a bug related to transformation of layer CRS from EPSG:3857 (Pseudo Mercator) to EPSG:4325 (WGS84 Geo).
I'm attaching a few images to demonstrate the issue.

Steps to reproduce:
I've load OSM in QGIS 2.18.16 (or 3.0,same results)
via Tile Server (XYZ):
https://a.tile.openstreetmap.org/{z}/{x}/{y}.png<https://a.tile.openstreetmap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png>

Then set the CRS to EPSG:4326 (WGS84 Geo)

I've also loaded a global bounds vector layer (EPSG:4326)

In scale 1:100,000,000 it seems that the Pseudo Mercator transformation to 4326 is flawed, as the OSM and the vectors are not aligned.
In scale 1:50,000,000 it seems OK when the extent is the middle of the map, but if I pan to the south/north it seems distorted again.

If I set the project CRS to EPSG:3857 (Pseudo Mercator) as the CRS of the OSM tiles, so the vector layer would be transformed instead, then they do align in all scales (picture with the blue vector layer).

It doesn't look like a problem of precision of the transformation from 3857 to 4325 because it's way off.
Is that a bug or am I missing something here?

Kind regards,
Idan.

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