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

[Idan Miara]

 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

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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180305/15f95eab/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: PseudoMercator.jpg
Type: image/jpeg
Size: 7441 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180305/15f95eab/attachment.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 50M_2.jpg
Type: image/jpeg
Size: 9380 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180305/15f95eab/attachment-0001.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 50M_1.jpg
Type: image/jpeg
Size: 17615 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180305/15f95eab/attachment-0002.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 100M.jpg
Type: image/jpeg
Size: 13651 bytes
Desc: not available
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20180305/15f95eab/attachment-0003.jpg>