DESCRIPTION

r.external.out instructs GRASS to write raster maps as data files (e.g. GeoTIFF) using GDAL.

NOTES

A relative directory path (parameter directory) is interpreted relative to the current mapset directory, not the current directory where the command was launched. An unspecified or empty directory (which will occur if the user passes a simple filename for output) results in the output file being placed in the "gdal/" subdirectory of the current mapset directory.

EXAMPLE

The module r.external.out can be used along with r.external to process external geodata in GRASS while writing out the results directly in GeoTIFF: 
# register GeoTIFF file to be used in current mapset:
r.external input=terra_lst1km20030314.LST_Day.tif output=modis_celsius

# define output directory for files resulting from GRASS calculation:
r.external.out directory=$HOME/gisoutput/ format="GTiff"

# perform GRASS calculation (here: extract pixels > 20 deg C)
# this stores the output map directly as GeoTIFF:
r.mapcalc "warm.tif = if(modis_celsius > 20.0, modis_celsius, null() )"

# cease GDAL output connection and turn back to write GRASS raster files:
r.external.out -r

# now use the resulting file elsewhere
gdalinfo $HOME/gisoutput/warm.tif

REFERENCES

GDAL Pages: http://www.gdal.org/

SEE ALSO

r.in.gdal, r.out.gdal, r.external

AUTHOR

Glynn Clements

Last changed: $Date$