Air Quality Modeling Analyses Transition from DEM to NED Elevation Data on March 20

The Iowa DNR Air Quality Bureau will stop using Digital Elevation Model (DEM) files, and start using National Elevation Dataset (NED) files beginning Friday, March 20. All dispersion modeling analyses submitted to the Department after March 20 must use the NED data. The transition is in response to the recent release of AERMAP version 09040, which is capable of processing the newer NED files.

Beginning March 20, NED files covering the entire state will be available on the Air Quality Bureau’s website at:

www.iowacleanair.com/prof/tech/ElevData.html.

DEM files will be removed from the website and will no longer be available.

The new data will be in county-sized files instead of the smaller quadrangle-sized format of the old DEM files. In most cases this change will allow users to simply import the file for the county in which the analysis is conducted. Multiple NED files may still be used in analyses along county borders.

Users should be aware that elevations derived by AERMAP using NED files may differ significantly from the elevations derived from the older DEM files. This change is due to the fact that the NED data is newer, and includes changes to topography since the original DEM files were created.

Questions or concerns regarding this transition may be directed to Brad Ashton at brad.ashton@dnr.iowa.gov, or by phone at (515) 242-6532.