How do I process a large file.  I tried help and searching this forum, but I can't figure this out.  Is there a way to process chunks of the file sequentially instead of the entire image?  Thanks, Dan File: Clipped a 2009 USDA raster .sid image of Montgomery Co, Ohio down to a 391M file of the City of Dayton. It is now in .img format.  Hardware: HP  xw8600 quad-core workstation with 16M of Ram.  Software, ENVI 4.7, ENVI EX, ENVI Zoom. Process: ENVI 4.7 Zoom -> Feature Extraction workflow. 

  I could not answer this question.  I think that there is also too much variability across the image for Feature Extraction to process accurately.  One can make out the suture-like borders of the adjacent collect paths in this mosaic image.   I have now used an existing set of shape files for the City of Dayton and run ArcMaps/ArcCatalogue, Spatial Analyst extension, Extraction, Extract by Mask (ie shapefile) [Tool only works if one navigates to it from ArcCatalogue, not ArcMap!!!]  I subsequently ran it again against each neighborhood.  

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Feature Extraction and Mask I now have smaller (.img) files with which to work.  These images are comprised of an irregularly shaped neighborhood surrounded by a broad border of black pixels.  I assume that this is a condition of raster formats being a rectangle of row and column pixels. Feature Extraction now runs in a reasonable amount of time, but it fails to produce any usable results.  Mostly it produces a single feature class for 99% of the image.  When I run Feature Extraction on a ‘chip’ of the data, then I get good polygons.  The chip has no border of black pixels.  Do I need a Mask to ignore these black pixels for Feature Extraction?  I have not been able to quite follow the Help file for Creating Masks.  Should I continue spending time on this strategy?  Is there any trick for pulling all of those black pixels out as the mask?