I would like to create a raster mosaic of the national USGS NED 30m DEM (~50 GB). I'd like to leverage parallel processing using python multiprocessing module where possible. I'm using ArcGIS 10.0. My first approach was divide and conquer - mosaic 2-10 at a time and then mosaic the result.

Q) What is the best method for mosaic parallization? Examples?

EDIT: the original two-part question was split into two questions. The other is here.


1 Answer 1


You can specify the parallel processing factor in the Mosaic environment settings (See attached image), which is new to ArcGIS 10.1 SP1. However, be cautious with this method since ESRI's documentation is very minimal and bordering on cryptic. I would do some timed runs (and share your findings here) before implementing these environment settings on very large datasets. Essentially, you can set the number of cores across which the tool spreads its operation. For example, if your machine has 4 cores and you specify "50%", the process will run on 2 cores, and so on. Again, a word of caution, as this may or may not optimize the processing--I've seen examples of both.

Regarding the edge errors, I have encountered the same problem when working within a file geodatabase (FGDB). I now primarily do raster processing outside of the FGDB and make sure the output results are .img files, as these tend to be a proven and reliable format.

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  • 2
    Note that the parallel environment was introduced at 10.1 SP1
    – KHibma
    Commented Jan 10, 2013 at 21:55
  • @KHibma Post edited to address comments.
    – Aaron
    Commented Jan 10, 2013 at 22:05
  • Glad to hear some parallel is implemented in 10.1.1, though I'm using 10.0. I've replicated my edge issue using different file formats and destinations. Tried inputs and outputs as .img, and storing and saving to file gdb's and system folders. Commented Jan 10, 2013 at 22:19
  • As another option, and as I specify in the post, try using arcpy.Mosaic_management().
    – Aaron
    Commented Jan 10, 2013 at 22:24
  • I'm not upgraded to 10.1 and have found the Parallel Processing Factor useful. However, I should note here that the parallel processing factor environment setting is not supported for arcpy.Mosaic_management(). See documentation here Commented May 22, 2013 at 18:02

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