[Qgis-user] GRASS and UK LIDAR

[Dave Marshall]

Nyall,

The first error which appears is "WARNING: Datum
<Unknown_based_on_Airy_1830_ellipsoid> not recognised by GRASS and no
parameters found ".I think all subsequent errors stem from this. This error
message occurs whether I choose a CRS transformation or not.

Cheers,

Dave

On Tue, 9 Feb 2021 at 02:05, Nyall Dawson <nyall.dawson at gmail.com> wrote:

> On Tue, 9 Feb 2021 at 05:57, Dave Marshall <43carnaby at gmail.com> wrote:
> >
> > Hello,
> >
> > I use QGIS 3.4 to visualise LIDAR tiles from the UK which use EPSG:27700
> as the CRS. I put height contours on the images using the r.contour feature
> in GRASS. This works extremely well. I have tried a couple of times to move
> to a more up-to-date version of QGIS but in each case, the version of
> r.contour associated with later versions does not work. These later
> versions seem to require some sort of co-ordinate transformation on opening
> the LIDAR files (I think to EPSG:4326) and I wonder if this is part of the
> problem. Running r.contour generates an error message which seems to
> suggest it does not recognise or cannot work with the CRS being used (there
> is a reference to Airy Spheroid).
>
> What's the error?
>
> Nyall
>
>
>
> >
> > What I would like to do is to be able to use a more up-to-date version
> of QGIS but with the same version of GRASS which I get when I use 3.4. This
> version would seem to be 7.6.1 rather than 7.8.5.
> >
> > There is a similar contour feature in QGIS under \Raster\Extraction but
> this does not allow the specification of height ranges which is essential
> for the work I am doing to avoid the routine from taking a very long time
> to run.
> >
> > Any help or advice would be much appreciated,
> >
> > Dave Marshall
> > _______________________________________________
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