Hi, I have developed an extension to Geoserver to expose IBM's searchable store of raster satellite data ( geospatially indexed in HBase) as a Geoserver raster layer. To the Geoserver client, the data appears as a new type of Geoserver DataStore which is published as a global geoserver layer. Multiple clients can request images through this new layer exposed by our extension/plugin using WMS protocol. This plugin function is implemented using the Geoserver/Geotools SPI Interfaces DataStoreFactorySpi and GridFormatFactorySpi. Then I extend AbstractGridCoverage2DReader to return a multiband GridCoverage2D to Geoserver when invoked through the GridCoverage2DReader.read(...) method. This extension has worked well for a couple years rendering dynamic images to the Geoserver client leveraging Geoserver to do SLD, WPS processing for us.
Recently however, I need to add support for WCS getCoverage() format to return a GeoTiff and am encountering an issue. A WCS getCoverage operation invokes the GridCoverage2DReader.read(...) in my extension extension in the same way as with WMS getMap. I'm called with an AbstractGridFormat.READ_GRIDGEOMETRY2D parameter with a request envelope that matches the 'subset' region on the WCS request. ( A sample GET request is below.) On the first WCS request after a Geoserver start I get a request envelope that is the WCS subset of the request. Lets say, as the sample request below, a 4 x 4 degree region in India. (Note, the extent property of the published layer in Geoserver layer is global (-180, -90) -> (180, 90)). I go get the data and hand back a GridCoverage2D with a raster for this region specifying the envelope of the data, ( i.e. the 4 x 4 degree box) . So far, all is good and the returned Geotiff looks fine in gdalinfo and when used as a QGIS data source. The problem is on the all subsequent WCS queries which are for a different subsets of the layer. For every subsequent request, the requestEnvelope that comes in AbstractGridFormat.READ_GRIDGEOMETRY2 is identical to what I returned in the first request, the 4x4 degree patch in India. The result is if there is no overlap between the subsequent request envelope in and that of the original query no data is returned. If there is some overlap between the original spatial subset and that of subsequent queries, the overlap is returned. From this behavior I see at a naive level that the intent of a WCS query is to get back the extant of the layer Coverage and then crop it down to the requested subset. Unlike a WMS request where I just hand geoserver a gridCoverage with the dat of the BBOX argument. It seems Geoserver is deciding after the first request that the extant of the coverage of the layer is limited to what I returned and keeping that info until I restart the Geoserver. There must be some information I am failing to provide in the return gridCoverage that lets Geoserver know I am only giving a small area back of the global coverage of the layer. And not to cache the extant as that of the entire layer. These are very high resolution images and at different timestamps. It is not possible to return the entire global raster coverage for Geoserver to crop down to the requested sub-region. I have tried turning off all the caches that I know of. I also suspect the solution may have something to do with the affine transform that is passed in on the request. But I don't have any ideas how to continue here. (Sample request, the parameters with 'ibmpairs' are custom extension indicating what raster data to fetch out of HBase). http://localhost:8080/geoserver/pairs/wcs?service=WCS&version=2.0.1&request=getcoverage&format=tiff&coverageid=pairs__pairspluginlayer&width=1920&height=960&ibmpairs_layerid=49523&ibmpairs_timestamp=1262304000&bbox=15,78,19,82&subset=Long(78,82)&subset=Lat(15,19)&SUBSETTINGCRS=EPSG:4326 Thanks for your help, Norm Norman Bobroff 914 945 2094 bobr...@us.ibm.com
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