Background
A DEM is a digital file consisting of terrain elevations for ground positions at regularly spaced intervals.
 
Distribution & Format
The GIS Service Bureau distributes DEMs in native format only. To decrease file size and transfer time, the native DEM files have been individually compressed into a Zip format. The files can be decompressed with any software that handles Zip files like Unzip, PKUnzip, or WinZip to name a few.
 
Download
DEMs for the State of Ohio can be downloaded for free.

DEMs are also available from the United States Geological Sruvey (USGS).

Web Address: http://geodata.oit.ohio.gov/geodatadownload/data.aspx