DEM/Grid Manipulation and Formats


NED DEM/grid Manipulate DEM Save/Export DEM
Every GIS program will have its own internal representation of the DEM.  This step converts other formats into the program's format.  The program then only has to deal with one way of doing things. The program can modify the DEM, create a new grid, or do map algebra with multiple grids.

Export can be in the GIS program's native format, or in an interchange format for use by other program. The export can be done of the File, Save DEM menu:

  • The full grid/DEM
  • A subset of the DEM.  This reduces the size, for reduced storage and faster display, by making the coverage area smaller.  This option will only appear is you have used the Subset & zoom option.
  • A thinned/decimated DEM.   This reduces the size, for reduced storage and faster display, by making the pixel size larger.  This is on the Raster GIS, Thin

USGS formats:

  • Geotiff: .TIF--need only the single file.  This is the best interchange format, supported by the most GIS programs.
  • Grid float:  select the .FLT and also need .HDR, and must keep the two together
  • .IMG--needs  GDAL for the singleIMG  file.
  • ArcGrid--needs  GDAL, and you need the entire directory, and pick the  "w001001.adf" file
 Internally uses the MICRODEM format. For continued use in MICRODEM, use its format.
For export to other software, the most robust format is Geotiff.

 New image or New Landcover map opens imagery, which we will generally see in Geotiff format.


last revision 9/5/2018