[QGIS-ZA-user] Gdal can't open output file

[Admire Nyakudya]

Hi Lawrence

On 2022/09/08 07:34, lawrence Sharpley via qgis-za-user wrote:
> gdal_contour -b 1 -a ELEV -i 10.0 -f "GPKG" 
> contextualWMSLegend=0&crs=EPSG:3857&dpiMode=7&featureCount=10&format=image/png8&layers=pyrbuild:contours_5m_sudem_wc&styles=pyrbuild:contours&tileMatrixSet=EPSG:3857&url=https://sungis08.stb.sun.ac.za/geoserver/gwc/service/wmts? 
> /tmp/contours.gpkg

In order for you to run the gdal_contour algorithm you need to have a 
DEM layer as Input. And from the parameters you have shared you are 
accessing a WMS layer and you won't have access to the individual values 
of the elevation layer. You need to check if the service has WCS exposed 
and load the layer into QGIS and save it out as a geotiff therefore 
acquiring the individual values of the DEM layer.

As for the layer permission issue I suggest you create a folder either 
in /tmp/ or in your home directory and make the folder owned by you like 
chown -R ${user}:${user} /tmp/output and executable chmod -R 777 
/tmp/output.

Regards

Admire
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