How to build mosaiced 1:250,000 DEMs

  1. In UNIX, access the EROS data center. 
             ftp edcftp.cr.usgs.gov
  2. Navigate to the appropriate directory (e.g., "F" for fresno-e). 
             cd /pub/data/DEM/250/F
  3. Get the data file. 
             binary
         get fresno-e.gz
         bye
  4. Unzip the data files. 
             gunzip fresno-e
  5. Redo steps 2 to 4 for all other desired files. 
             .
         .
         .
         gunzip bakersfield-e   
         gunzip death_valley-w  
         gunzip trona-w
  6. In ArcInfo, generate the individual file DEMs. 
             arc
         demlattice fresno-e fresno_e
         demlattice bakersfield-e bakersfield_e
         demlattice trona-w trona_w
         demlattice death_valley-w d_valley_w
  7. In GRID, mosaic the adjacent files together. 
             grid
         panamint = mosaic(fresno_e,d_valley_w,trona_w,bakersfield_e)
         quit
  8. In Unix, construct a projection file called ds_to_dd.prj and add in the following lines. 
             Input
         Projection    GEOGRAPHIC
         Datum         WGS72
         Zunits        METERS
         Units         DS
         Spheroid      WGS1972
         Xshift        0.0000000000
         Yshift        0.0000000000
         Parameters
         Output
         Projection    GEOGRAPHIC
         Datum         WGS72    
         Zunits        NO      
         Units         DD     
         Spheroid      WGS1972
         Xshift        0.0000000000
         Yshift        0.0000000000
         Parameters
         End
  9. In ArcInfo, project the grid from decimal-seconds to decimal-degrees (the DEM data come from the Eros Data Center in decimal-seconds). 
             arc
         project grid panamint panamint_dd ds_to_dd.prj
  10. In GRID, display the grid. 
             grid
         display 9999 3
         mapextent panamint_dd
         image panamint_dd


11/08/99