"rotating" raster maps

Rick Thompson rick at cast.uark.edu
Fri Nov 5 14:08:05 EST 1993

> I am importing some ascii files as rasters which need to be transformed
> so that the rows become columns and columns become rows.  I have examined
> m.rot90 but this seems to work only with generic ascii files and not
> GRASS raster maps.

First, uncompress the grass raster file with r.compress -u. Specify the number
of bytes per cell (found in the cellhd for the file). If the format is 0, then
it is 1 byte per cell (nbytes is format + 1). The input file must be placed in 
a different mapset out of the present search path, and a new cellhd file needs
to be made which reflects the altered rows and columns (Don't forget to change
the region, too, to reflect the changes in rows/cols).  Finally, mv the colr, 
cell_misc, and cats files to the new file name. Both m.flip and m.rot90 work
this way. Compress the files when completed.

Rick Thompson-   Research Assistant           E-mail: rick at cast.uark.edu
Center for Advanced Spatial Technologies      Telephone: (501) 575-5736
Ozark Hall Rm. 12                             Fax: 575-3846 
University of Arkansas              
Fayetteville, AR 72701

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