These DEM's are 1:1,000,000 composites of the 1:250,000 DEM's available from USGS.  They are centered on the state for which the file is named, of course.  The files are in ESRI's ARC export format.  They are .e00 files.  The .e00 files, when imported into ARC, ArcView, etc., contain ARC GRID format versions of the DEM's.  They are in Latitude and Longitude.


The following steps were taken to generate the variety of dems in these directories (please excuse the change of tense between steps six and seven) :

1) The original 1:250,000 1 degree dems were downloaded from
   edcftp.cr.usgs.gov in netscape 6.2.  You have to click on each
   one degree file individually, which takes a little time.  I used
   the download by STATE option to make sure I got all the quads for
   the state in question.  I got the compressed files.

2) The 1 degree files were then secure ftp'd to gilbert using Linda 
   Garinger's profile (from pc under clock). 

3) The files were copied to /slate/mono5/sbrmd/xxdem, where xx is the
   abbreviation for the state.

4) The files were gunzip'ed    gunzip *.gz

5) The files were imported into Imagine
   Import/Export  file type USGS Dem  (these are NOT SDTS, luckily)
   You have to click on each file individually, which takes a little time.

6) The files were mosaiced using Data Preparation/Mosaic
   Add (the page looking icon in the upper right)
   Select file (need to select one), then where it says individual file,
   click and select All Files in Directory.
   Wait until the outline of the files pop up in the other window.
   Click on Process to actually do the mosaic.
   Save both the output image mosaic and the .mos mosaic control file.

7) Open a viewer, open a raster input,select the mosaiced image.  
   On the menu bar, click on Raster/Geometric correction.
   You are not really going to geometrically correct the image, just
   getting to the resampling tool.

8) Click on Close on Affine in the Geometric correction window.  When
   the affine transformation window opens, the little window with the 
   resampling tool will open separately (it looks like a little pink 
   four pane window).  Close the Geometric correction window.  

9) Click on the resampling tool.  Pick the output file name.  On the
   two small elongate text boxes near the bottom that say '1', click
   on the up arrows to make them '2'.  This will resample from
   1:250k to 1:500k.  Click ok.  The new image will be resampled.

10) Repeat 7 thru 9 starting with the 1:500k image to get to 1:1000k.

11) Export each 1:1000k image as a GRID.

12) To clip to state boundaries.  Get ESRIdata's states.shp.
    Edit it in Arcview so you get a shape file for each state.
    In ARC run shapearc on the shape file, then  run build on 1the coverage.
    In GRID (not ARC) run gridclip on the grid using the state coverage
    as the clip_cover.  You done.

Unless, you want to merge all the DEMS.  Just mosaic them in Imagine.
    Convert the shape file to a coverage.