[Qgis-user] Arctic data distortion when crossing the 180° meridian (EPSG:3996 vs EPSG:3857)

[Vedran Stojnović]

Hi,

currently, the best solution is to generate a very small buffer around
North-South line at meridian location and then you cut (remove) your
geometry at the location of that buffer.
This will avoid problems with rendering, it will be visible only if zoomed
in to very large scale.

So the steps are:
1) generate or draw North-South line
2) generate very small buffer around it
3) cut your geometries with buffer to generate a small gap at meridian
location

See video where I've explained how to avoid this problem when using custom
meridian location:
https://www.youtube.com/watch?v=5M-Q0AinuiY&t=3560s

You can download GPKG file with project that includes models and data so
you see steps in my model how i solved it:
https://github.com/qgis/QGIS/wiki/QOD-July-2025#topic-teaching-projections-in-classroom-with-qgis---workshop

Srdačan pozdrav / Kind regards,
Vedran Stojnović.


sri, 11. ožu 2026. u 08:17 김용운 빙하지권연구본부 via QGIS-User <
qgis-user at lists.osgeo.org> napisao je:

>
> Hello,
>
> I am working with Arctic Ocean datasets in QGIS and would like to ask for
> advice regarding CRS handling and geometries crossing the 180° meridian.
>
> For Arctic data, I normally use EPSG:3996 (WGS 84 / Arctic Polar
> Stereographic) as the project CRS. In QGIS Desktop, this works well and
> produces the expected visualization for tracks and stations (Figure 1).
>
> However, when I try to use these datasets in a web mapping context, I am
> forced to switch the project CRS to EPSG:3857. With this change, datasets
> that cross the 180° meridian (anti-meridian) show problematic behavior:
> - line features are split and displayed at both sides of the map,
> - and in some cases the geometries appear distorted or disconnected
> (Figures 3 and 5).
>
> The original geometry itself is correct (Figure 4), so the issue seems to
> be related to CRS transformation and rendering rather than data corruption.
>
> I tested several CRS combinations, and the following produced the closest
> alignment:
> - Project CRS = EPSG:3857
> - Layer CRS = EPSG:3996
>
> Nevertheless, the anti-meridian splitting issue remains unresolved. I also
> tried suggestions found in documentation and online discussions (e.g.
> reprojection, geometry fixes, alternative basemaps), but none solved the
> problem fundamentally.
>
> Since many Arctic datasets naturally cross the 180° meridian, I would
> greatly appreciate advice on:
> - best practices for handling Arctic/polar data in QGIS,
> - recommended CRS strategies when working near the anti-meridian,
> - or preprocessing steps that can prevent line splitting and visual
> discontinuities.
>
> Thank you very much for your time and any suggestions.
>
> Best regards,
>
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