[QGIS-Developer] Slow WCS processing and Clipping WCS by extent not working

[Raymond Nijssen]

Just uploaded a processing script for downloading WCS, as a work around 
for this problem:

https://hub.qgis.org/scripts/17/

But hopefully it can be fixed in QGIS somehow. Any ideas anyone?

Raymond


On 8/14/26 08:29, Raymond Nijssen via QGIS-Developer wrote:
> Created an issue too:
> https://github.com/qgis/QGIS/issues/67061
> 
> 
> On 8/14/26 07:02, Raymond Nijssen via QGIS-Developer wrote:
>> Dear developers,
>>
>> Currently I'm working on a process that uses a WCS service containing 
>> elevation data. I need 800x800m pieces from the elevation raster.
>>
>> My graphical model uses a Raster Calculator algorithm, with one of the 
>> (2) layers being the WCS layer from my project. This works but is very 
>> slow. It takes about 1 minute to process the 800x800m calculation.
>>
>> If I download the raster using gdal_translate, it only takes 2 seconds 
>> or so. I cannot find out what the Raster Calculator is doing differently.
>>
>> On top of that, I need to do calculations for the same area 3x, so 
>> every location takes up over 3 minutes, and my entire process with 
>> many locations over 6 hours.
>>
>> So I had some ideas to speed this up, but so far they all have 
>> downsides and I'm not sure what is the best way to proceed:
>>
>> 1. Using the Raster Calculator with only one layer and storing the 
>> output for the next 3 calculations. Will still take 1 minute extra, 
>> but is more effective (and a bit lame).
>>
>> 2. Using the Clip Raster by Extent algorithm, which seems perfect for 
>> this. But it does not work for WCS, cause it parses the QGIS layer 
>> source string directly into gdal_translate but GDAL needs another 
>> string and throws an error. Looking at the Python source code, this 
>> has probably never worked for WCS.
>>
>>    2a. Fixing the Clip Raster by Extent algorithm. Cause it is in 
>> Python, I can give it a try. But I already found out that the Clip 
>> Raster by Mask algorithm has the same issue. And maybe more raster 
>> algorithms do. So that should be solved in less redundant way, right?
>>
>>    2b. Asking a core developer to rewrite this properly in c++. Maybe 
>> in a way that uses the QGIS network manager so the http-calls get 
>> shown in the debugging panel? No idea what this would cost but I think 
>> I can get this funded somehow.
>>
>> 3. Making my own Python WCS downloader algorithm in Python (I think I 
>> will need to do this anyway to deliver my project on time, but I 
>> prefer more long term solutions for all QGIS users.)
>>
>> Any suggestions?
>>
>> Kind regards,
>> Raymond
>>
>>
>>
>>
>> Some data
>>
>>
>> This is the GDAL command QGIS generates to clip the extent (2) and the 
>> error:
>>
>> GDAL command:
>> gdal_translate -projwin 148100.0 412300.0 148900.0 411500.0 -of GTiff 
>> "cache=AlwaysNetwork&crs=EPSG:28992&format=GEOTIFF&identifier=dsm_05m&url=https://service.pdok.nl/rws/actueel-hoogtebestand-nederland/wcs/v1_0" /tmp/processing_NXPMbm/6597707893384cf9b74c2603ab45909d/OUTPUT.tif
>> GDAL command output:
>> ERROR 4: 
>> cache=AlwaysNetwork&crs=EPSG:28992&format=GEOTIFF&identifier=dsm_05m&url=https://service.pdok.nl/rws/actueel-hoogtebestand-nederland/wcs/v1_0: No such file or directory
>> Process returned error code 1
>>
>>
>>
>>
>> This is the working WCS, url generated by QGIS and copied from the 
>> debugging panel:
>>
>> https://service.pdok.nl/rws/actueel-hoogtebestand-nederland/wcs/v1_0? 
>> SERVICE=WCS&VERSION=1.0.0&REQUEST=GetCoverage&FORMAT=GEOTIFF&COVERAGE=dsm_05m&BBOX=142327.30414899752940983,408519.58202700602123514,156029.62145483330823481,415020.39733971789246425&CRS=EPSG:28992&RESPONSE_CRS=EPSG:28992&WIDTH=704&HEIGHT=334
>>
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