I have a 5m DEM for an entire province in Spain. It is over 48gb in size and is in asc file format. I only need a very small, 50 km² area.

I open the DEM in ArcDesktop, and i get the loading bar for hours.

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    If you know the extent (xmin, ymin, xmax, ymax) you can use Clip Management resources.arcgis.com/en/help/main/10.1/index.html#//…, I'd recommend converting to something else.. ASCII is a horrible format (XYZ is worse). Copy Raster resources.arcgis.com/en/help/main/10.1/index.html#//… would do that for you but is still likely to take hours. Is your data on a slow/network drive? Hours seems a little extreme. I notice that your pyramids aren't built - you could build pyramids to help loading. GDAL_translate would also be good here. May 26, 2016 at 5:06
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    ASCII to raster should is 1st step. Next step is set environment Extent and use raster calculator. Might try Extent first, ASCII>raster after
    – FelixIP
    May 26, 2016 at 5:12
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    With gdal_translate I would do gdal_translate -of GTiff -co tiled=yes -co compress=deflate andalusien_dem.asc andalusien_dem.tif Assign projection with -a_srs if GDAL does not recognize it from .asc file, check with gdalinfo. Clipping parts of the converted tiff will be fast with gdal_translate and other tools. If you want to open the tiff file with desktop create overviews with gdaladdo but for clipping it is not needed.
    – user30184
    May 26, 2016 at 6:20
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    @user30184 and FelixIP have the right ideas. Convert that into something more efficient first. If you do need to open it in Desktop, open a clean instance and load in a layer that covers your area of interest. Zoom in to that area, then add the DEM. Doing this will restrict the amount that has to be processed, though that format may be inefficient enough that it has to read it all before it can narrow it down. May 26, 2016 at 6:55
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    First of all, avoid using ArcMap. Loading / displaying such a huge raster isn't a great idea. Try using ArcCatalog straigth away with the functions metioned above (ascii to raster). Second, as other users already suggested, convert your raster. I'd personally create a file GDB and load the raster dataset into it. The clipping should then become manageable.
    – dru87
    May 26, 2016 at 11:27

1 Answer 1


@FelixIP has the correct answer.

My issue was that the dataset couldnot be processed on my perosnal workstation, with 8 GB of RAM. It required a powerstation with 128GB of RAM.

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