Merge NED

• Copy the .FLT and .HDR files, or the Geotiffs, or the MICRODEM DEMS,  into the same directory.  Note that the tile files have sensible names, and are unique.  This is not always the case with Seamless Server data, which is a random fairly large number.
• If you had to get IMG or ArcGrid files, insure you have GDAL, and open each file in turn, and then  File, Save DEM, MD DEM, and place the .DEM files all in the same directory.
• File, Open, Open and merge DEMs, and pick the FLT, TIF, or MICRODEM format files.  If you are unable to merge because the files are too large, try this.
• Database Database (shapefile) for the shapefile TIGER data.
• Subset & zoom so that you cover all of the county, but not a lot of extra area.
•  File, Save DEM, Current subset, MD DEM.  Give it a meaningful name, and put in a directory where you can find it.
• Close merged DEM. 
• NED DEM Open the subset DEM

last revision 1/31/2017