GeoServer GetCoverage with a specific resolution

Question

I have a GeoServer serving GeoTIFFs as WCS. I would like to get a slice (bbox) of a coverage at a specific resolution.

MapServer seems to support this:

WIDTH=output_width: Width in pixels of map picture. One of WIDTH/HEIGHT or RESX/Y is required.

HEIGHT=output_height: Height in pixels of map picture. One of WIDTH/HEIGHT or RESX/Y is required.

(source: https://mapserver.org/de/ogc/wcs_server.html)

If I add this to my WCS request, it is ignored:

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http://192.168.37.10:8080/geoserver/wcs?request=GetCoverage&coverageId=ml__Duesseldorf&height=512&width=512&service=WCS&version=2.0.1&subset=E(355017.6407251246,355761.0022115205)&subset=N(5679871.219933263,5680544.231752177)

This returns the TIFF in the same spatial resolution as in the source data.

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adding scalefactor=0.25 works:

http://192.168.37.10:8080/geoserver/wcs?request=GetCoverage&coverageId=ml__Duesseldorf&scalefactor=0.25&service=WCS&version=2.0.1&subset=E(355017.6407251246,355761.0022115205)&subset=N(5679871.219933263,5680544.231752177)

This works but I can only scale the whole image, while I would like to set a specific resolution. for example: height=51 width=512

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Also I wonder if there is any documentation for GeoServer WCS that explains all the parameters that can be used?

(bbox for example also doesn't work as well)

Answer 1

SCALESIZE can be used to set the size of a of request. This is defined in:

OGC® WCS Interface Standard - Scaling Extension, version 1.0.0

The spec defines the kvp for Scal::ScaleToSize as SCALESIZE=a1(s1),…,an(sn) For my usecase this means that the KVP has to look like this:

SCALESIZE=i(512),j(512)

with the full request:

http://192.168.37.10:8080/geoserver/wcs?request=GetCoverage&coverageId=ml__Duesseldorf&SCALESIZE=i(512),j(512)&service=WCS&version=2.0.1&subset=E(355017.6407251246,355761.0022115205)&subset=N(5679871.219933263,5680544.231752177)

Note that the name of the axis is the abbreviation of the axis, while subset requires the full names.

These names can be extracted from a DescribeCoverage request:

...
<wcs:CoverageDescriptions ...>
  <wcs:CoverageDescription>
    <gml:boundedBy>
      ...

      <gml:Envelope ... axisLabels="E N">


      </gml:Envelope>
    </gml:boundedBy>
    ...
    <gml:domainSet>
      <gml:RectifiedGrid>
        ...

        <gml:axisLabels>i j</gml:axisLabels>


    </gml:domainSet>
    ...
  </wcs:CoverageDescription>
</wcs:CoverageDescriptions>