[qgis-qwc2] Issue publishing Arctic project in EPSG:3996 with QWC2 (CRS not defined & anti-meridian splitting)

[김용운 빙하지권연구본부]

Hello,

I am working on publishing a QGIS project to QWC2 in order to share Arctic Ocean datasets in a web environment.

Because my datasets are located in the Arctic, I normally use EPSG:3996 (WGS 84 / Polar Stereographic) as the project CRS in QGIS. In desktop QGIS, this CRS works correctly and produces the expected visualization (Figure 1).

However, when publishing the project to QWC2, the theme fails to load and QWC2 reports that “the projection EPSG:3996 is not defined” (Figure 2). Due to this limitation, I changed the project CRS to EPSG:3857 so that the project can be loaded in QWC2.

With this workaround, I encounter serious rendering issues for datasets crossing the 180° meridian (anti-meridian):
- line and track features are split and rendered at both edges of the map,
- and in some CRS combinations the geometries appear heavily distorted (Figures 3 and 5).

For reference, these are the main configurations I tested:
- Desired QGIS desktop view:
  Project CRS = EPSG:3996, Layer CRS = EPSG:4326 (Figure 1)
- QWC2 workaround configuration:
  Project CRS = EPSG:3857, Layer CRS = EPSG:3996 (Figure 3)

I tried multiple CRS combinations, but this setup provided the closest overall alignment in QWC2, although the anti-meridian splitting problem remains. I also tested several approaches suggested in documentation and online resources (e.g. tile-based basemaps, geometry correction), but none resolved the underlying issue.

Since many of my Arctic datasets cross the 180° meridian, this problem affects a large portion of the data and prevents producing a visually continuous map.

Could you please advise on:
- whether EPSG:3996 can be properly supported in QWC2, or
- the recommended workflow for publishing Arctic (polar) data in QWC2 without visual discontinuities at the anti-meridian?

Any guidance regarding CRS configuration, QGIS Server / QWC2 settings, or preprocessing strategies would be greatly appreciated.

Thank you very much for your help.

Best regards,



[https://bigfile.kopri.re.kr/readreceipt2.ashx?id=YzcwMzA5Y2EtMzhmZi00N2E4LThiMmMtMDVlMWQ0ZDZlY2M1]
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