[Qgis-user] GRASS and UK LIDAR

[Nyall Dawson]

On Wed, 10 Feb 2021 at 00:20, Dave Marshall <43carnaby at gmail.com> wrote:
>
> 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.

Ok - that's an error coming straight from GRASS itself. You'll need to
ask the GRASS project about this one and raise a ticket on their issue
tracker!

Nyall

>
> 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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