<div dir="ltr">Thanks everyone for the explanations; they were very helpful and insightful.<div>Regards, </div><div>Gabriel</div><div><br></div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Fri, Jun 27, 2025 at 8:35 AM Richard Duivenvoorde <<a href="mailto:rdmailings@duif.net">rdmailings@duif.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Gabriel,<br>
<br>
Disclaimer: a lot of GEO-nerds here, he :-)<br>
<br>
But: given the perimeter on the equator of the earths is about 40000 km, as you can see in your image, the scale bar is 'sort of valid' on the equator, but totally OFF if you look near the poles (where the perimeter of the earth is probably a fraction of the 10000 km scale).<br>
<br>
So: in general in such (global) maps you should not use a scalebar, but on local level (where you use proper crs's and the unit's are meters), you SHOULD always use a scalebar :-)<br>
<br>
And yes: do blame Matlab for his error from us ;-)<br>
<br>
Regards,<br>
<br>
Richard Duivenvoorde<br>
<br>
On 27-06-2025 12:55, Gabriel Cotlier via QGIS-User wrote:<br>
> Thanks to all. I currently have installed QGIS 3.34. I do not know the validity of this map from MATLAB at : <a href="https://la.mathworks.com/help/matlab/ref/geoaxes.html" rel="noreferrer" target="_blank">https://la.mathworks.com/help/matlab/ref/geoaxes.html</a> <<a href="https://la.mathworks.com/help/matlab/ref/geoaxes.html" rel="noreferrer" target="_blank">https://la.mathworks.com/help/matlab/ref/geoaxes.html</a>><br>
> but I was thinking of a map like this one, just without the small map in the upper right corner and the division of countries in QGIS. I do not know if that woud be possible and if so, if that scale bar in the figure below makes any sense?<br>
> Thanks a lot again.<br>
> <br>
> <br>
> image.png<br>
> <br>
> On Fri, Jun 27, 2025 at 2:22 AM Andreas Neumann <<a href="mailto:andreas@qgis.org" target="_blank">andreas@qgis.org</a> <mailto:<a href="mailto:andreas@qgis.org" target="_blank">andreas@qgis.org</a>>> wrote:<br>
> <br>
> Hi all,<br>
> <br>
> Chris explained why it is impossible to have a consistent scale for a world projection on a 2D flat plane.<br>
> <br>
> The good news is, that in QGIS 3.44 there is a setting to influence the scale calculation method: see <a href="https://www.qgis.org/project/visual-changelogs/visualchangelog344/#application-and-project-options" rel="noreferrer" target="_blank">https://www.qgis.org/project/visual-changelogs/visualchangelog344/#application-and-project-options</a> <<a href="https://www.qgis.org/project/visual-changelogs/visualchangelog344/#application-and-project-options" rel="noreferrer" target="_blank">https://www.qgis.org/project/visual-changelogs/visualchangelog344/#application-and-project-options</a>><br>
> <br>
> Best regards,<br>
> Andreas<br>
> <br>
> On Fri, 27 Jun 2025 at 02:37, chris hermansen via QGIS-User <<a href="mailto:qgis-user@lists.osgeo.org" target="_blank">qgis-user@lists.osgeo.org</a> <mailto:<a href="mailto:qgis-user@lists.osgeo.org" target="_blank">qgis-user@lists.osgeo.org</a>>> wrote:<br>
> <br>
> Gabriel and list,<br>
> <br>
> <br>
> <br>
> On Thu, Jun 26, 2025, 16:05 Gabriel Cotlier via QGIS-User <<a href="mailto:qgis-user@lists.osgeo.org" target="_blank">qgis-user@lists.osgeo.org</a> <mailto:<a href="mailto:qgis-user@lists.osgeo.org" target="_blank">qgis-user@lists.osgeo.org</a>>> wrote:<br>
> <br>
> Dear QGIS Users,<br>
> 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.<br>
> <br>
> 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? <br>
> <br>
> <br>
> 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.<br>
> <br>
> This entails some serious distortion of the surface of the earth.<br>
> <br>
> You are hoping for a projection that preserves distances at all points on the map.<br>
> <br>
> You may wish to read this Wikipedia article on map projections.<br>
> <br>
> <a href="https://en.m.wikipedia.org/wiki/Map_projection" rel="noreferrer" target="_blank">https://en.m.wikipedia.org/wiki/Map_projection</a> <<a href="https://en.m.wikipedia.org/wiki/Map_projection" rel="noreferrer" target="_blank">https://en.m.wikipedia.org/wiki/Map_projection</a>><br>
> <br>
> 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.<br>
> <br>
> <br>
> Chris Hermansen · clhermansen "at" gmail "dot" com<br>
> <br>
> C'est ma façon de parler.<br>
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> Andreas Neumann<br>
> <a href="http://QGIS.ORG" rel="noreferrer" target="_blank">QGIS.ORG</a> <<a href="http://QGIS.ORG" rel="noreferrer" target="_blank">http://QGIS.ORG</a>> board member (treasurer)<br>
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</blockquote></div>