[Qgis-user] GRASS and UK LIDAR

[Dave Marshall]

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 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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