U. S. Geological Survey Open-File Report 2004-1229A

ARC/INFO Grid Export format 
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This format is readable by ARC/INFO, ERDAS IMAGINE, ARC/VIEW, and 
other packages. When imported into ARC/INFO and ARC/VIEW, the file 
will unpack into a directory containing all the components of the 
registered grid coverage.   The ARCGRID module in ARC/INFO
and SPATIAL ANALYST in ARC/VIEW will allow display in color shaded- 
relief.