Hi Richard,
I don't know about the QGIS side, but from the server side I'd agree
with your assessment.
The WCS 1.0 spec says that the server will use the interpolation method
specified in the getcapabilities (or if none is defined (as here), then
assume Nearest Neighbour) for alternative widths/heights.
Having to interpolate an entire country down to a 10x10 grid seems
utterly bonkers for a WCS. Even WMS (where you will have overviews so
it'll be massively faster) I can't think of why you'd want a tiny 10x10
output.
Maybe this is QGIS's way of trying to creating a WCS legend icon?
Whatever the reason, I'd suggest raising it as a bug report as it's not
going to be doing any favours to the WCS servers for no real benefit.
Cheers,
Jonathan
On 2018-10-12 11:48, Richard Duivenvoorde wrote:
Hi,
using our national DEM WCS:
https://geodata.nationaalgeoregister.nl/ahn3/wcs?
Loading the layer ahn3_5m_dtm for an area of a couple of km in
epsg:28992 is very slow.
I'm not so familiar with the WCS specs, but I see QGIS asking:
https://geodata.nationaalgeoregister.nl/ahn3/wcs?SERVICE=WCS&VERSION=1.0.0&REQUEST=GetCoverage&FORMAT=GEOTIFF_FLOAT32&COVERAGE=ahn3_5m_dtm&BBOX=10000,250000,356250,618750&CRS=EPSG:28992&RESPONSE_CRS=EPSG:28992&WIDTH=10&HEIGHT=10
which is the whole of the Netherlands (in a 10x10 pixel output??) and
after that a more proper bbox.
Is this supposed to go like this?
I reckon that (if the WCS data does not have overviews), loading the
whole dataset all the time is pretty intensive.
Anybody more familiar with this can tell something about this?
Regards,
Richard Duivenvoorde
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