Polygon on Raster query in GeoServer - geoserver

Question

I need to perform a polygon on raster cookie-cut and pixel sum using GeoServer. The polygon (GeoJSON) and raster are both in WGS84 (4326). The raster is a very large GeoTIFF population raster published with GeoServer. I have two questions:
How to do the entire operation in GeoServer?
Alternatively, how to query the raw pixel values from the rectangular extent of the polygon (minx, miny, maxx, maxy), and I can do the pixel in/out sum analysis myself.
I have tried WMS queries and WCS queries but cannot find a way to request the raw pixel values rather than a PNG rendered result. I have also tried some WPS sample queries, with no success. I'm not seeing much from Google on polygon-on-raster statistics. Is this entire query possible in GeoServer? Or is at least fetching a rectangular area of raw pixels from the GeoTIFF from GeoServer possible?
Thanks!!

Answer 1

To fetch a rectangle of pixels as a GeoTiff you would need to use a WCS request. The easiest way to define one of those is using the WCS Request generator - for example:
<?xml version="1.0" encoding="UTF-8"?><GetCoverage version="1.0.0" service="WCS" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wcs" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xsi:schemaLocation="http://www.opengis.net/wcs http://schemas.opengis.net/wcs/1.0.0/getCoverage.xsd">
<sourceCoverage>nurc:Pk50095</sourceCoverage>
<domainSubset>
<spatialSubset>
<gml:Envelope srsName="EPSG:32633">
<gml:pos>347649.93086859107 5176214.082539256</gml:pos>
<gml:pos>370725.976428591 5196961.352859256</gml:pos>
</gml:Envelope>
<gml:Grid dimension="2">
<gml:limits>
<gml:GridEnvelope>
<gml:low>0 0</gml:low>
<gml:high>545 490</gml:high>
</gml:GridEnvelope>
</gml:limits>
<gml:axisName>E</gml:axisName>
<gml:axisName>N</gml:axisName>
</gml:Grid>
</spatialSubset>
</domainSubset>
<output>
<crs>EPSG:32633</crs>
<format>GeoTIFF</format>
</output>
</GetCoverage>
To extract values of a raster bounded by a polygon you can use a WPS request to crop to a polygon and then sum the pixels yourself:
<?xml version="1.0" encoding="UTF-8"?><wps:Execute version="1.0.0" service="WPS" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wps/1.0.0" xmlns:wfs="http://www.opengis.net/wfs" xmlns:wps="http://www.opengis.net/wps/1.0.0" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xmlns:wcs="http://www.opengis.net/wcs/1.1.1" xmlns:xlink="http://www.w3.org/1999/xlink" xsi:schemaLocation="http://www.opengis.net/wps/1.0.0 http://schemas.opengis.net/wps/1.0.0/wpsAll.xsd">
<ows:Identifier>ras:CropCoverage</ows:Identifier>
<wps:DataInputs>
<wps:Input>
<ows:Identifier>coverage</ows:Identifier>
<wps:Reference mimeType="image/tiff" xlink:href="http://geoserver/wcs" method="POST">
<wps:Body>
<wcs:GetCoverage service="WCS" version="1.1.1">
<ows:Identifier>nurc:Pk50095</ows:Identifier>
<wcs:DomainSubset>
<ows:BoundingBox crs="http://www.opengis.net/gml/srs/epsg.xml#32633">
<ows:LowerCorner>347649.93086859107 5176214.082539256</ows:LowerCorner>
<ows:UpperCorner>370725.976428591 5196961.352859256</ows:UpperCorner>
</ows:BoundingBox>
</wcs:DomainSubset>
<wcs:Output format="image/tiff"/>
</wcs:GetCoverage>
</wps:Body>
</wps:Reference>
</wps:Input>
<wps:Input>
<ows:Identifier>cropShape</ows:Identifier>
<wps:Data>
<wps:ComplexData mimeType="application/wkt"><![CDATA[POLYGON((x1 y1, x2 y2,......))]]></wps:ComplexData>
</wps:Data>
</wps:Input>
</wps:DataInputs>
<wps:ResponseForm>
<wps:RawDataOutput mimeType="image/tiff">
<ows:Identifier>result</ows:Identifier>
</wps:RawDataOutput>
</wps:ResponseForm>
</wps:Execute>
Or you could write your own custom process to carry out the whole process in one go.