Hi Richard Thanks for testing it. I don't know if it is an issue or a feature (not kidding. It could be a simplification to be faster, with a way to disable it somewhere in the settings). That's why I asked here in the mailing list, not in github. I just want to know the reason. My workaround is to reproject with ogr2ogr.
Please, let me know the issue number when you create it. I can add there any needed extra information. Thanks, Javier. On Wed, 23 Jul 2025 at 14:44, Richard Duivenvoorde via QGIS-User < [email protected]> wrote: > Mmm, funny :-) > > I can reproduce this. > > So only with the 'Identify features' popup shown, the second line seems to > be rendered??? > > As if the rendering of the mapcanvas is different then the rendering of > 'rubberband'... > > I would create an issue (with a small screencapture of the hovering, > because it took me some time to figure out what you meant :-) ) > > Regards, > > Richard Duivenvoorde > > > > On 22-07-2025 16:50, Javier Jimenez Shaw via QGIS-User wrote: > > Hi > > > > I am trying to compare web-mercator (EPSG:3857) with Mercator > (EPSG:3395) projections. > > For that purpose I think that a straight line in EPSG:3395 (loxodromic) > shouldn't be exactly straight in EPSG:3857. > > > > To show that, I created two linestrings in EPSG:3395, one with one > segment, and the second with two segments co-linear (just adding a point in > the middle). If I then select EPSG:3857 in QGIS, there should be a small > difference... but I do not see it! > > > > Only if I use the "Identify features", click in the area (at the proper > zoom level), and hover over "identify all" or "2p". Then a second line > appears! But it disappears when I select anything. (see attached screenshot) > > > > The attached gpkg files are just the geometries as one segment (2p.gpkg) > and 2 segments (3p.gpkg), both defined in EPSG:3395 > > > > The coordinates of the line are (0,0) and (8e6, 10e6) Yes, a long line > to make it more visible. > > the midpoint in EPSG:3395 is (4e6, 5e6). That is easy. > > > > Reprojecting the two points into EPSG:3857 we have (0,0) and > > > > echo 8e6 10e6 | cs2cs EPSG:3395 EPSG:3857 > > 8000000.00 10039255.88 0.00 > > > > The midpoint is > > echo "scale=2; 8000000.00 / 2; 10039255.88 / 2" | bc > > 4000000.00 > > 5019627.94 > > > > The midpoint in EPSG:3395 and then projected to EPSG:3857 is this: > > echo 4e6 5e6 | cs2cs EPSG:3395 EPSG:3857 > > 4000000.00 5028099.31 0.00 > > > > The difference is about 8 km. But I cannot see it in QGIS. > > > > Jakub suggested that it could be the simplification. I disabled it in > the settings. No difference. > > > > Is QGIS doing something strange? Can I disable it? > > > > If I select EPSG:4326 instead of EPSG:3857, then you can see clearly the > two linestrings. > > > > Thanks, > > Javier. > > > > > > _______________________________________________ > > QGIS-User mailing list > > [email protected] > > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > > _______________________________________________ > QGIS-User mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >
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