Hi all, Chris explained why it is impossible to have a consistent scale for a world projection on a 2D flat plane.
The good news is, that in QGIS 3.44 there is a setting to influence the scale calculation method: see https://www.qgis.org/project/visual-changelogs/visualchangelog344/#application-and-project-options Best regards, Andreas On Fri, 27 Jun 2025 at 02:37, chris hermansen via QGIS-User < [email protected]> wrote: > Gabriel and list, > > > On Thu, Jun 26, 2025, 16:05 Gabriel Cotlier via QGIS-User < > [email protected]> wrote: > >> Dear QGIS Users, >> I have been trying to do a world map with a scale bar and found the >> problem that needs a global projection, such as Greenwich for instance then >> the "scale bar" displayed in the map of the layout is for instance, 0.2 m >> in length but visually not consistent at all with the size of the >> continents and distances of the world map displayed. >> >> How could a world map with a scale bar be produced such that the scale >> bar length and size look consistent with the length and size of a world map >> in QGIS? >> > > Gabriel, the usual problem with trying to do a scale bar on a global map > is that you have projected the spherical (more or less) globe onto a flat > map. > > This entails some serious distortion of the surface of the earth. > > You are hoping for a projection that preserves distances at all points on > the map. > > You may wish to read this Wikipedia article on map projections. > > https://en.m.wikipedia.org/wiki/Map_projection > > Another visual device that one sometimes sees is several "stacked" scale > bars, one for each 10 degrees or so of latitude, which of course isn't > feasible when the two points to be measured are at different latitudes. > > > Chris Hermansen · clhermansen "at" gmail "dot" com > > C'est ma façon de parler. > _______________________________________________ > 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 > -- -- Andreas Neumann QGIS.ORG board member (treasurer)
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