Didger imports elevation data in the form of a uniform lattice from SDTS Digital Elevation Model .DEM data sets.
There are two separate types of SDTS DEM files. The Topological Vector Profile SDTS files contain boundary line information. The Raster Profile SDTS files contain gridded elevation information.
It is not necessary to unzip the .TAR.GZ, .TAR, .ZIP, or .TGZ file. Didger can read the information in the various files directly from the compressed file.
If you do unzip the .TAR.GZ, .TAR, .ZIP, or .TGZ file containing the DDF files, there is an option in WinZip (or other unzipping software) that needs to be disabled. Use the WinZip settings to disable this option. All .DDF files must be extracted into the same directory.
In WinZip, use the Options | Configuration command to open the Configuration dialog.
Click on the Miscellaneous tab.
In the Other category, un-check TAR file smart CR/LF conversion.
Click the OK button.
The Tar.GZ file will now properly unzip the files.
Format(s) Supported for Import
2D uniform lattice; 8-, 16-, 32-bit integer, float, double
Import Options Dialog
No import options dialog is displayed.
Export Options Dialog
Didger does not currently export this file format.
USGS Digital Elevation Model File Description
File Format Chart