Understanding the ESRI Binary Grid format (aka - what're all those files in the folder?)

I get this question regarding the GeoEarthScope "standard" DEMs on a regular basis, so I am going to address it here for everyone:

I have downloaded some of Northern California GeoEarthScope LiDAR DEM tiles in Google Earth. For every single grid, there are two folders with different *.adf files. Can you please clarify what are the files of *.adf format?

First, for each zip file downloaded from either the Google Map or KML (Google Earth) interfaces, there are two DEM files - a bare earth (vegetation removed) and a full feature (vegetation, buildings, etc. still present). The bare earth DEMs are prepended with "fg" (for "filtered grid") and the full feature are preprended with "ug" (for "unfiltered grid"). For example:

When you download file 443_4443.zip and uncompress it, it contains two directories:
fg443_4443
ug443_4443

Inside each of these directories are these files:
dblbnd.adf
hdr.adf
log
prj.adf
sta.adf
w001001.adf
w001001x.adf

Basically, the ESRI Binary Grid format (aka Arc/Info Binary Grid) is the collection of the files listed above. ArcGIS treats the directory containing the files as the grid (DEM). So, when you attempt to load fg443_4443 into ArcGIS, the software sees that directory as a single DEM, not as a directory containing other files. For more information on the file format and to learn more about what each of the files above is, take a look at these links:

http://support.esri.com/index.cfm?fa=knowledgebase.techarticles.articleShow&d=30616
http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=About_the_ESRI_grid_format
http://home.gdal.org/projects/aigrid/aigrid_format.html

Software other than ArcGIS (Global Mapper for example) does not see the whole directory as a single DEM and instead requires that you point it towards the appropriate *.adf file. In this case, you need to navigate into the fg443_4443 directory to the w001001.adf file in order for the software to load the DEM.

Finally, if you don't have access to software that will read the ESRI binary grid format, GDAL (http://www.gdal.org/) is an excellent and free tool that will allow you to convert these files into a format that is compatible with whatever software you are using.