I'm using Openlayers3 and GeoServer 2.9.1 to create an application allowing users to draw an aoi then download it as raw data subsets (geotiff) of a Canada wide data set (also geotiff). I'm using a WCS 1.0.0 GetCoverage request where bbox and Grid Dimensions are dynamically entered.
When validating the subsets, a simple subtraction of the downloaded data from the original dataset reveals pixel value changes (see image). How can I retrieve raw data subsets without re-sampling errors? It is critical that the pixel values be identical to the original.
Making a GetCoverage request from GeoServer's Demo Request Builder using the same bbox coords as my script gives me the same errors.