[Qgis-user] Using r.contour with QGIS 3.12

[Christoph Jung]

Hello Dave,

I am not very familiar with the grass tools and its error messages. But as an alternative you could use gdal_contour to generate contour lines from a raster layer. 

Sincerely,
Christoph

> Am 09.04.2020 um 00:05 schrieb Dave Marshall <43carnaby at gmail.com>:
> 
> 
> Hello,
> 
> I've just upgraded to 3.12 from 3.4 and when working with LIDAR data I find that r.contour no longer works. The first warning which occurs is: Datum <Unknown_based_on_Airy_1830_ellipsoid> not recognised by GRASS and no parameters found  
> Further error messages are: Datum <Unknown_based_on_Airy_1830_ellipsoid> not recognised by GRASS and no parameters found
> 
> WARNING: Unable to open vector map <output4a2f59f8cf014c4d8b8b782e7d15854a at PERMANENT> on level 2. Try to rebuild vector topology with v.build.
> ERROR: Unable to open vector map <output4a2f59f8cf014c4d8b8b782e7d15854a>
>  and finally a message saying the layers were not correctly generated. 
> This routine worked perfectly in version 3.4.
> 
> Is there a simple fix? I am using OSGB 1936 / British National Grid [EPSG:27700] as CRS.
> 
> Thanks,
> 
> Dave Marshall
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