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I am working with thousands of DEM tiles, so I have put them into a Mosaic Dataset. (Please give me feedback if this is not the best way to handle this amount of data).

I was given DEM tiles that extend beyond the area of interest, so I did a Select by Location in order to choose the footprints that fall within the area of a particular polygon.

I have tried right clicking the "Image" title in the Mosaic Dataset and choosing Export data (with Selected Footprints). This returned a raster with all of the rasters in the Dataset.

EDIT I have tried Exporting the data from the Mosaic Dataset twice. Once using a Mask and again using Extents (all in Geoprocessing Environments). For both I used a polygon I created. Yet the output is still the full raster.

Background geoprocessing is turned off, so I can't figure out what is going wrong so far.

How do I go about creating a raster from of the area of interest?

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  • You can use your mosaic and selected tiles as inputs to slice tool with polygon option.
    – FelixIP
    Commented Mar 2, 2018 at 2:44

3 Answers 3

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Your choice of mosaic dataset is a very acceptable way of handling lots of image files, I use them frequently for just this sort of thing and have found them to be as useful as a single, mosaiced, raster but much quicker to create. You can also use rasters located in many different folders to create a mosaic dataset without needing to copy them all to a single location, a real drive space benefit, as only the overviews need to be stored on the same drive as the mosaic dataset.

The most serious drawback to using this raster storage method is that only Esri software can access mosaic datasets. Should you need to create a mosaic-dataset-like object which is usable outside of Esri there is the GDAL VRT dataset which is an XML file recognized by Esri, QGIS etc.. One of these can be created with GDALBuildVRT. This virtual storage type is significantly slower at redrawing and exporting than a mosaic dataset so I would only recommend using it outside of Esri; it is possible though to link the rasters in both a mosaic dataset and a virtual dataset (VRT) as neither format is exclusive.

You can handle exporting your mosaic dataset to another format with a reduced extent in one of two ways: geoprocessing environment Mask and/or geoprocessing environment Extent.

If you have a polygon shapefile you're interested in you can use both the extent and mask to reduce the size of the export and to trim off any areas you're not interested in within the extent rectangle of the feature class. Otherwise, if you're only interested in exporting the raster that is overlapping existing data or a known extent you only need to set the Extent environment, either by specifying an existing feature class or raster or by manually entering the extent to export within.

I have found it best to ensure that all coordinates for extent and mask are in the same coordinate system as the 'to' raster.

If you are overlaying your output raster with another look also at Snap Raster and Cellsize to ensure pixel-by-pixel alignment.

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  • I have tried Exporting Data from the mosaic dataset using both Mask and Extent in the geoprocessing environment, yet the output is still the full sized raster. Do you have any suggestions about what is going on?
    – MoreMeowbell
    Commented Mar 2, 2018 at 15:37
  • How/when are you setting the environments? On the bottom of the Raster to Other Format resources.arcgis.com/en/help/main/10.2/index.html#//… tool dialog there is an environments button, set your parameters there - this sets the parameters for this tool only and does not affect your global settings, you also know that the environments apply to this instance; If you read the tool help, down the bottom, there is a list of which environment settings apply to the tool, not every setting applies to all tools. The mask setting may only apply if you have spatial analyst.
    – Michael Stimson
    Commented Mar 4, 2018 at 21:58
  • I set the environment on the Tool. I have all of the Arc extensions, so that shouldn't be a problem. It just seems like the Mosaic Dataset won't honor any Extent or Mask environments I set.
    – MoreMeowbell
    Commented Mar 5, 2018 at 22:27
  • That is so odd, which tool are you using to convert the mosaic dataset into a raster dataset? Raster to Other Format resources.arcgis.com/en/help/main/10.2/index.html#//… and Copy Raster resources.arcgis.com/en/help/main/10.2/index.html#//… specifically state that they honor the Extent setting; I have tested both with a mosaic dataset and found that both did export a subset, using ArcGIS 10.2.1. You could try Clip_management resources.arcgis.com/en/help/main/10.2/index.html#//… to extract a subset of the mosaic dataset.
    – Michael Stimson
    Commented Mar 5, 2018 at 22:41
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    Clip_management takes a mosaic dataset as an input as at 10.2.1.
    – Michael Stimson
    Commented Mar 7, 2018 at 0:05
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After some research. I have found the answer to my origional question. It is possible to create a raster from only selected footprints in a Raster Mosaic Dataset.

  1. Select footprints for raster
  2. Right click Footprints in Table of Contents
  3. Choose Lock to Selected Footprints
  4. Right click Image (part of Mosaic Dataset) in Table of Contents
  5. Export Data
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  1. Select footprints for raster
  2. Right click mosaic dataset in table of contents.
  3. Choose 'selection', then 'attribute table showing selection'.
  4. Use field calculator to calculate a unique value for the field 'GroupName'.
  5. Open the geoprocessing tool 'Export Mosaic Dataset Items'.
  6. Add a definition query that filters only the unique group name from step4.
  7. Run the geoprocessing tool.
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