Where can I obtain seamless DEM data from the USGS?
A. Seamless DEM data available from the USGS National Elevation Dataset web site at http://seamless.usgs.gov/ can be downloaded at no cost providing the file sizes remain under a specified size, generally 100 MB. File larger than the limit are written to CDR and shipped for a modest price. Follow the prompts for View and Order Data Sets selecting either United States or International. For the US, a National Map will appear – alternatively either click, hold down cursor and drag an area on the map to select your area of interest, or, preferably, click on Define Area by Coordinates found in the left panel towards the bottom of the screen. This approach allows a specific quad to be selected and enables exact matches when combining multiple map resources. Confirm the selected area. When the SDDS Request Summary Page appears, click Modify the Request to specify the format, altering the ArcGrid format to BIL for the selected NED – National Elevation Dataset, and choosing ZIP for the download
