11.G.viii. Importing into ESRI's Arc/INFO

Users of Arc/INFO can import GLOBE DEM and source/lineage files (GUNZIP decompressed) by converting the DEM to an Arc/INFO grid with the command IMAGEGRID. Importing the northwestern (file a10g) tile of GLOBE into Arc/INFO is presented as an example.

• Copy a10g.hdr (Arc/INFO ASCII header file described in Section 11.F.iv), a10g.clr (Arc/INFO ASCII color palette file described in Section 11.F.iv), and a10g (binary elevation data) files into your Arc/INFO workspace. Rename the file a10g to a10g.bil. You should now have the following files in your ArcInfo working directory: a10g.bil, a10g.hdr, and a10g.clr.
• Next, from within Arc/INFO run IMAGEGRID:

  imagegrid a10g.bil a10gaig
  

• To add projection information to a10gaig, at the Arc prompt type the following:

  projectdefine grid a10gaig
  

  This begins an interactive dialog for entering projection information for the data set. At the Project prompt, enter the following information. The word "parameters" completes the projection definition.

                       projection geographic
                       units dd
                       datum wgs84
                       zunits meters
                       parameters
  

• IMAGEGRID does not support conversion of signed image data, therefore the negative 16-bit DEM values will not be interpreted correctly. After running imagegrid and adding the projection information, this can be fixed by using the following formula in GRID:

  a10gconv = con(a10gaig >= 32768, a10gaig - 65536, a10gaig)
  

  where a10gaig is the file created by imagegrid, and a10gconv is the converted signed integer grid. This process creates a georeferenced Arc/INFO GRID file called a10gconv. You can use the resultant GRID file in Arc/INFO's GRID module. The converted grid will then have the negative values properly represented, and the statistics of the grid should match those listed in Table 3 (Section 11.C). This step is not necessary when importing source/lineage files from the source/data directory since these files contain 8-bit values.

• If desired, the -500 ocean mask values in the grid could then be set to NODATA with the SETNULL function in GRID:

  a10gnull = setnull(a10gconv == -500, a10gconv)
  

• To display the file with the color palette provided, copy the a10g.clr file (color palette file) to your Arc/INFO workspace. Then use the following commands in ARCPLOT:

                      display 9999
                      mape a10gnull
                      gridpaint a10gnull # # # a10g.clr
  

  The zero and negative values are all displayed as black.