Hello, I do a lot of work with UK LIDAR data and one of the most frequently used, and useful, GRASS routines for my work is r.contour. I am currently using GRASS through QGIS 3.4.12 and the associated version of GRASS is 7.6.1. I have made a couple of attempts to upgrade my QGIS version to a more recent one but this always results in a different version of GRASS which does not allow r.contour to work with the LIDAR files.
QGIS 3.4 opens LIDAR tif files directly using EPSG:27700 as the CRS. Later versions of QGIS seem to require, or at least suggest, a transformation to an alternative CRS. Whether I use one of these transformations or not, the initial error I receive when running r.contour is "WARNING: Datum <Unknown_based_on_Airy_1830_ellipsoid> not recognised by GRASS and no parameters found". Other errors follow and finally there is a message to say that the routine has failed. I think that all the versions of GRASS which have generated this error are 7.8. I would like to upgrade my version of QGIS to a later version but am stuck with 3.4 because of my need for a functioning r.contour. QGIS contains a similar contour-drawing option but it does not allow the specification of upper and lower height limits and so can take a very long time to run on large files. Any help or advice will be much appreciated, Dave Marshall
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