Nationwide Guide to USGS DEMs

1. SRTM DEMs

The Shuttle Radar Topography Mission (SRTM) is a joint project between NASA and NGA (National Geospatial-Intelligence Agency) to map the world in three dimensions.

"Finished" quality data can be obtained from seamless.usgs.gov. Those data still contain void (zero elevation) areas where no altitude measurement was obtained.

Post-corrected "Finished" quality data with interpolated void (zero) gaps were made available by Martin D. Adamiker at the California and Nevada - Overview page.

2. 3 arc second DEMs

Get a zipped file dem_250.zip (71 kB) containing information about all USGS quadrangles. The file contains the data as a tabstop separated ASCII file and as a Microsoft Excel sheet (very cool for sorting by latitude and longitude!).

Note: as of March 28 1997, the coordinates UL LON and UL LAT specify the upper left corner of the respective quadrangle in accordance to all of our navigational help systems.

Sample lines:

STATE  DEM NAME      UL LONG UL LAT DATE     URL1
-------------------------------------------------
SD,ND  ABERDEEN - E  -99.00  46.00  01/29/87 http://...
SD,ND  ABERDEEN - W -100.00  46.00  01/29/87 http://...

The present file layout was chosen by us for our latest software project: TFMAKE, the interactive terrain visualization system. Just specify the coordinates, and downloading and rendering will take place automatically.

3. 30 meter DEMs

Nationwide coverage where available: Tables containing the quadrangle names of the USGS 30 meter DEMs.

Note: These tables contain no URLs - there is no online access due to the massive amount of data involved. However, we established online access via TFMAKE for:

• California thanks to the University of Northridge
• Pennsylvania thanks to the Penn State Earth System Science Center
• West Virginia thanks to the Office of Surface Mining
• Washington thanks to the University of Washington

Each ZIP file contains the data as a tabstop separated ASCII file and as a Microsoft Excel sheet. The coordinates in the header row and column specify the upper left corner of the respective quadrangle.

We decided to use the name "30 meter DEMs" throughout this website instead of "7.5 minute DEMs", since in Alaska there are also 15 minute quadrangles.