Instructions provided describe how to convert GTOPO30 DEM data into a grid. Use ArcInfo GRID to convert a USGS GTOPO30 DEM to grid format while retaining the digital elevation data values.
Click the link in the Related Information section to download a GTOPO30 DEM. This file comes as a .TAR file, which contains the *.dem and *.hdr files. Both files are required for this operation.
out_grid = CON(in_grid >= 32768,in_grid - 65536,in_grid)
out_grid2 = SETNULL(out_grid == -9999,out_grid)