OHD/HL/DMIP - DEM

DEMs of two different resolutions are now available from this page -- 15 arc-second DEM data and 1 arc-second DEM data.  The current DMIP project design does not require the use of any particular DEM.  These DEM data are provided for convenience, but participants are welcome to use any DEM data that are available to them.

15 arc-second DEMs

These data represent sampled elevations at regularly spaced, 15 arc-second (0.0041666 degrees) intervals, in geographic coordinates.  The National Operational Hydrologic Remote Sensing Center (NOHRSC) created a 15 arc-second national DEM by resampling 3 arc-second DEMs (1:250,000 scale) distributed by the U.S. Geological Survey.  The 15 arc-second data available through this web site are for clipped windows, which cover the DMIP study basins.

The 15 arc-second data files are in ASCII format.   The first several lines of these files contain spatial referencing information:

nrows = number of rows
ncols = number of columns
xllcorner, yllcorner = coordinater for the lower left corner of the lower left cell
cellsize (units are decimal degrees)
NODATA_value

Data following the header information are listed in row-major order with the top (northernmost) row on the first line.
Elevation units are meters.

For users of ESRI software, data can be imported into Arc/Info using the "asciigrid" command or imported in to the ArcView Spatial Analyst using the File --> Import Data Source option.

Clicking on one of the following links will download an ASCII file with data covering the specified geographic region.

· Illinois River Basin
· Cheat River Basin

1 arc-second (30-m) DEMs (from USGS NED project)

30-m data covering the DMIP study areas have been made available for this project as an offshoot of the National Basin Delineation project underway at NOAA's National Severe Storms Laboratory (NSSL).  The primary goal of the National Basin Delineation project is to provide small basin boundaries for the National Weather Service Flash-flood Monitoring and Prediction Program (FFMP).  To produce the small basin boundaries, NSSL is cooperating with the USGS EROS data center to use the 1 arc-second DEM data available from the USGS National Elevation Dataset (NED) project  (http://edna.usgs.gov/).

NSSL is organizes their data processing efforts by eight digit USGS Hydrologic Cataloging Unit (HUC) boundaries.  Initial processing steps include:
(1) buffering the HUC boundary of interest to allow for differences in ridgelines defined by the DEM and defined by the digitized HUCs
(2)  merging the required 7.5 minute blocks of DEM data into a seamless data set covering the HUC of interest
(3) projecting the seemless data set to allow for correct analysis using Arc/Info software
(4) "filling" the DEM to eliminate artificial sinks (using the Arc/Info fill command)

The filled DEMs (product of Steps 1 through 4) for HUCs covering the DMIP basins are made available below.  The main data files accessible from the links below are in ASCII format and have been compressed using gzip.  The eight digit HUC numbers are used to name the files.

11110103.asc.gz -- Illinois River at Watts, OK; Baron Fork at Eldon, OK; Illinois River at Tahlequah, OK
11110103.prj

11070208.asc.gz -- Elk River at Tiff City, MO;
11070208.prj
11140102.asc.gz -- Blue River at Blue, OK
11140102.prj
05020004.asc.gz -- Cheat River at Parsons, WV
05020004.prj

The first 6 lines of the unzipped files linked above contain the same header information described above for the 15 arc-second data; however these data are projected and the cellsize = 30 meters.  The projection information and Zunit information for these grids is available in the .prj files.

Data following the header information are listed in row-major order with the top (northernmost) row on the first line.

For users of ESRI software, data can be imported into Arc/Info using the "asciigrid" command or imported in to the ArcView Spatial Analyst using the File --> Import Data Source option.

The original 7.5 minute DEM data are available from the U.S. Geological Survey: http://edcwww.cr.usgs.gov/doc/edchome/ndcdb/ndcdb.html (7.5 minute quadrangle data)