[QGIS-Developer] Geometry generator expression for line segment length

[Anita Graser]

On Mon, Nov 18, 2019 at 4:40 AM Nyall Dawson <nyall.dawson at gmail.com> wrote:

> On Fri, 15 Nov 2019 at 05:34, Anita Graser <anitagraser at gmx.at> wrote:
> >
> > Hi,
> >
> > I recently noticed that the expression I used in
> https://anitagraser.com/2016/10/09/movement-data-in-gis-2-visualization/
> does not work in current QGIS versions anymore. Specifically, I computed
> the metric length of a line segment by transforming from WGS84 'EPSG:4326'
> to 'EPSG:54027':
> >
> > length(
> >       transform(
> >         geometry_n($geometry, at geometry_part_num),
> >         'EPSG:4326','EPSG:54027'
> >         )
> >     )
> >
> > While debugging, I found that the transformation is not applied anymore.
> (Some other EPSG codes do work though.) However, I couldn't figure out how
> to get this transformation to work again.
>
> Is this a proj 6 based build? In any case, EPSG:54027 doesn't exist.
> The correct code is "ESRI:54027" (see https://epsg.io/54027).


Good catch, different four letters starting with E! The issue appeared on
OSGeo4W so I'll have to check if that means proj6 already. Anyway, I'll
give the other code a try!

Thanks
Anita




> It's
> possible that < proj 6 builds had some exception in place for this
> particular CRS, but with a proj 6 based build we rely on proj to
> interpret CRS auth/id pairs so any exceptions in place for earlier
> QGIS versions won't apply anymore.
>
> Nyall
>
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