Unable to load HYCOM ocean currents WCS layers in QGIS

Question

I'm attempting to load HYCOM ocean currents model WCS layers into QGIS.  QGIS is able to access the server and the available layers at "https://wcs.hycom.org/thredds/wcs/GLBy0.08/latest?version=1.0.0".  QGIS is able to connect and retrieve the available layers, but reports the following error when attempting to add the layer:
"Invalid Layer: WCS provider Cannot get test dataset. Raster layer Provider is not valid (provider: wcs, URI: cache=PreferNetwork&crs=OGC:CRS84&dpiMode=7&format=GeoTIFF_Float&identifier=water_u_bottom&time=2020-08-17T12:00:00Z&url=https://wcs.hycom.org/thredds/wcs/GLBy0.08/latest?version%3D1.0.0"
I've attempted multiple HYCOM datasets with varying layer formats with no success.

nmtoken · Answer

This looks like an error in the service, not in the ability of QGIS to access the service.

https://wcs.hycom.org/thredds/wcs/GLBy0.08/latest?service=WCS&version=1.0.0&request=DescribeCoverage&Coverage=water_u_bottom&

A describe coverage request on the water_u_bottom coverage shows an invalid CRS (EPSG:0 [Latitude_Longitude]):

<gml:RectifiedGrid srsName="EPSG:0 [Latitude_Longitude]" dimension="3">
    <gml:limits>
        <gml:GridEnvelope>
            <gml:low>0 0 0</gml:low>
            <gml:high>4499 4250 39</gml:high>
        </gml:GridEnvelope>
    </gml:limits>
    <gml:axisName>x</gml:axisName>
    <gml:axisName>y</gml:axisName>
    <gml:axisName>z</gml:axisName>
    <gml:origin>
        <gml:pos>0.0 -80.0 0.0</gml:pos>
    </gml:origin>
    <gml:offsetVector>0.08000000976779562 0.0 0.0</gml:offsetVector>
    <gml:offsetVector>0.0 0.04 0.0</gml:offsetVector>
    <gml:offsetVector>0.0 0.0 128.2051282051282</gml:offsetVector>
</gml:RectifiedGrid>

Note that the reference to urn:ogc:def:crs:OGC:1.3:CRS84 here is a reference to the description of the envelope, not to the CRS.

When you try to load a coverage, QGIS uses a default CRS (OGC:CRS84) to give a GetCoverage request like:

https://wcs.hycom.org/thredds/wcs/GLBy0.08/latest?SERVICE=WCS&VERSION=1.0.0&REQUEST=GetCoverage&FORMAT=GeoTIFF_Float&COVERAGE=water_u_bottom&TIME=2020-08-18T12:00:00Z&BBOX=0,-80,359.9200439453125,90&CRS=OGC:CRS84&RESPONSE_CRS=OGC:CRS84&WIDTH=10&HEIGHT=10

But the server replies with an HTTP 400.

You can access the service in QGIS if you use a full GetCoverage request without any CRS, as a raster layer specifying an HTTP/S connection instead of a file, like:

https://wcs.hycom.org/thredds/wcs/GLBy0.08/latest?SERVICE=WCS&VERSION=1.0.0&REQUEST=GetCoverage&FORMAT=GeoTIFF_Float&COVERAGE=water_u_bottom&TIME=2020-08-18T12:00:00Z&BBOX=0,-80,359.9200439453125,90&

Unable to load HYCOM ocean currents WCS layers in QGIS

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