[Qgis-user] Help with scales in print layouts for geographic CRS

[Greg Troxel]

Patrick Dunford via Qgis-user <qgis-user at lists.osgeo.org> writes:

> On 6/04/22 11:34, Greg Troxel via Qgis-user wrote:
>> Jorge Gustavo Rocha via Qgis-user <qgis-user at lists.osgeo.org> writes:
>>
>> 2) Using a geographic CRS, the same 150mm x 150mm map, at the same
>>> 1:10000 scale, the area is bigger then the 1500m polygon. The result
>>> is attached https://nextcloud.geomaster.pt/index.php/s/H2eAytsPANyxn6Y
>>>
>>> On both layouts the scale bar widget is working properly. The
>>> distances (and areas) are properly calculated in QGIS interface. I
>>> have set the GRS 1980 ellipsoid for distance and area calculations.
>> What does it mean to use a geographic CRS for a print layout?  Do you
>> really expect longitude on the x axis and latitude on the y axis?  The
>> value of meters/degree is different for x and y, unless you are at or
>> near the equator.  (Living at 42N-ish, I'm very aware of this.)
>
> This may be the case for projections like EPSG:3857 that are based on
> a spherical projection of the Earth but is it the case for all
> projections?

By "geographic CRS", I interpet that to mean one that is latitude and
longitude.  That is not really a "projection".

Yes, EPSG:3857 has an incorrect spherical assumption, and I'd have to
calculate, but I would not expect massive scale distortion, where
massive is casually visually apparent.

Perhaps Jorge can be precise about which CRS codes are in use.
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