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

[Idan Miara]

Thanks for you reply,
Since the problem exist also in 2.18 I don't think it is related with PROJ
5.0, Right?

On 5 Mar 2018 12:39, "Kristian Evers" <kreve at sdfe.dk> wrote:

> If you are using PROJ 5.0.0 it is likely to be caused by this known issue:
>
> https://github.com/OSGeo/proj.4/issues/834
>
> /Kristian
>
> -----Oprindelig meddelelse-----
> Fra: Qgis-user [mailto:qgis-user-bounces at lists.osgeo.org] På vegne af
> Benjamin Ducke
> Sendt: 5. marts 2018 10:18
> Til: qgis-user at lists.osgeo.org
> Emne: Re: [Qgis-user] Pseudo Mercator(OSM) @ EPSG:4326 bug?
>
> Could it be this:
>
> http://proj4.org/faq.html#changing-ellipsoid-why-can-t-
> i-convert-from-wgs84-to-google-earth-virtual-globe-mercator
>
> ?
>
> The further you get from the equator, the more
> obvious the discrepancy on the Y axis.
>
> Best,
>
> Ben
>
> On 05/03/18 09:38, Idan Miara 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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> >
>
>
>
> --
> Dr. Benjamin Ducke
> Deutsches Archäologisches Institut (DAI)
> Zentrale Berlin, IT-Referat
> * Projekt "Stunde Null" *
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