Hi Markus, You are also completely right! Some of data I exported (elevation, slope, aspect) did not have NULL cells. And in the other data that have NULLs, I used r.null to ensure that the NULL value was -9999. With that I simply transformed the NULL cells to the value -9999, wich are exported as a value and not as a NULL.
I see now that the GRASS behaviour is the correct, because it uses NODATA_value when the input raster contains cells with NULL value, and omits that parameter when the input raster does not contain any NULL cell. I was somehow mistaken because it seems that other software use NODATA_value as a default parameter, and for instance Farsite and FlamMap, where I use the data exported from GRASS, did not work well without the NODATA_value in the ASCII files, even if the input data has no NULL cells. Thank you very much! Best regards, Pedro 2017-08-04 9:52 GMT+01:00 Markus Neteler <nete...@osgeo.org>: > Hi Pedro, > > I created a test case with the North Carolina sample dataset (by > zooming in the GUI to the elevation map border and setting that as > computational region): > > # GRASS 7.2.2svn (nc_spm_08_grass7):~ > > > # set computational region around east elevation map border > g.region n=216820 s=216770 w=644960 e=645040 res=10 -p > > # be sure that no data pixels are involved. > r.out.ascii input=elevation output=- > north: 216820 > south: 216770 > east: 645040 > west: 644960 > rows: 5 > cols: 8 > 101.913734 102.054886 102.395638 102.597229 * * * * > 101.821335 102.044083 102.331108 102.58638 * * * * > 101.703033 101.955849 102.195648 102.54126 * * * * > 101.56945 101.840988 102.152328 102.529175 * * * * > 101.530174 101.792572 102.097748 102.477859 * * * * > > # export to AAIGrid format: > r.out.gdal input=elevation output=elev.grd format=AAIGrid > Driver <AAIGrid> does not support direct writing. Using MEM driver for > intermediate dataset. > Checking GDAL data type and nodata value... > 100% > Using GDAL data type <Float32> > Input raster map contains cells with NULL-value (no-data). The value -nan > will be used to represent no-data values in the input map. You can specify > a nodata value with the nodata option. > Exporting raster data to AAIGrid format... > 100% > r.out.gdal complete. File <elev.grd> created. > > > # verification: > cat elev.grd > ncols 8 > nrows 5 > xllcorner 644960.000000000000 > yllcorner 216770.000000000000 > cellsize 10.000000000000 > NODATA_value -nan > 101.91373443603515625 102.0548858642578125 102.39563751220703125 > 102.59722900390625 -nan -nan -nan -nan > 101.8213348388671875 102.0440826416015625 102.33110809326171875 > 102.5863800048828125 -nan -nan -nan -nan > 101.703033447265625 101.95584869384765625 102.195648193359375 > 102.541259765625 -nan -nan -nan -nan > 101.56945037841796875 101.8409881591796875 102.1523284912109375 > 102.5291748046875 -nan -nan -nan -nan > 101.53017425537109375 101.792572021484375 102.097747802734375 > 102.4778594970703125 -nan -nan -nan -nan > > ... all fine and it works out of the box! > Are you sure that you had any NULL cells at all? Note that the current > computational region is respected for export. > > Markus >
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