I've downloaded some USGS DEMs from the National Map, which appear to be .adf files. I can open them in ArcMap 10.2, but I need to merge them into a single mosaic. To do this, I've created a raster catalogue inside a geodatabase file, but when I try to 'Load rasters from workspace', the files are not visible.

Not sure what to do next. The files are clearly Esri-compatible (I can load and view them individually), but the steps to create a mosaic seem unable to read the files.

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    Would you be able to edit your question to include a link to the "similar question posted here in 2013", please? That way potential answerers can better understand what you have already tried. Does "doesn't seem to recognize" mean that an error is thrown? If so, including the text from that is likely to be valuable information for us to have. – PolyGeo May 27 '15 at 0:13
  • Unfortunately DEM is both a generic term and a specific file format. Do you have .dem files? nationalmap.gov/viewer.html seems to indicate that the DEM data is already in a raster format, in which case you just need to mosaic to new raster. It's not entirely clear what you've downloaded. – Chris W May 27 '15 at 1:44
  • Mosaic is another one of those terms with multiple meanings. You can mosaic several rasters to a new one, as we've been talking about (see resources.arcgis.com/en/help/main/10.2/index.html#//…). You can also create a mosaic dataset, which is a kind of virtual image made up of the smaller individual input images as tiles. In some ways/cases it's treated like a single image, but it actually isn't. – Chris W May 27 '15 at 20:37

The conversion toolbox has a tool to convert your DEM file to a raster format. Do that first, for each DEM. Then use the "Mosaic to new Raster" tool to combine them into a single file.

You'll want to be double sure each file you want to combine is in the same coordinate system/projection and the same units. I once had a particularly odd looking hillshade from a couple DEMs I merged where adjacent tiles were in feet and meters...

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  • Thanks for responding, Kevin. I've tried using the DEM-to-Raster tool, but it doesn't recognize the file, or any of the many files produced when I unpacked the .zip file downloaded from the National Map. – ColaGreg May 27 '15 at 17:04
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    If they're ADF files then they're most likely in ESRI grid format - which is a raster format from the start. Have you tried mosaicing the ADF files and skipping the conversion step? – Kevin May 27 '15 at 17:22
  • Yes - the problem is the same. When I try to 'Load Rasters from Workspace', ArcMap doesn't see or recognize the files. – ColaGreg May 27 '15 at 17:44
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    Just to clarify - the mosaic tool you want to use is called "Mosaic to New Raster" and it's located in Data Management --> Raster --> Raster Dataset. The first argument is called "Input Rasters" not "Load Rasters from Workspace" so I'm wondering if you're looking at the wrong tool. – Kevin May 27 '15 at 18:24
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    Yes! The 'Mosaic to New Raster' tool recognized the files and successfully created the mosaic. For the USGS DEMs, the number of bands is one and the pixel type is 32 bit, floating point (this info was needed to use the tool). Thanks Kevin! – ColaGreg May 27 '15 at 22:58

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