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11.D. Digital Elevation Data File Format

Files ?10G and ?10B ("?" is the wildcard notation for tile letters "A" through "P") are provided as 16-bit signed integer data in a simple binary raster. There are no header or trailer bytes embedded in the image. The data are stored in row major order (all the data for row 1, followed by all the data for row 2, etc.). All files have 10800 columns, and either 4800 or 6000 rows (see Table 3 in Section 11.C). The following diagram depicts the organization of the files:

       bytes1/2.................................bytes21599/21600
       bytes21601/21602.........................bytes43199/43200
       .........................................................  
       .........................................................  
       etc.
       ................................(last byte-1)/(last byte)

The data are in little-endian byte order (that is, for IBM-compatible PCs, Digital Equipment VAXes, etc.) UNIX workstations using big-endian byte order can swap bytes using the command:

dd if=inputfilename of=outputfilename conv=swab

where "inputfilename" and "outputfilename" are replaced with the user’s selection of input and output file names.

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