[GRASS-user] Export of GeoTIFF

[Maciej Sieczka]

christian.braun at tudor.lu wrote:

> I have serious problems exporting GRASS DCELL rasters to GeoTIFF.
> I used r.out.gdal with type=Float32 and set the compression to LZW. 
> What I got later on in ArcView 3.3 is pure noise fort he picture and in 
> ArcGIS 9.2 I get some strange results.
> The NULL values of the picture get a cryptic code like -1#QUAN1 and if 
> there are pixels with value 0 they become NoData in ArcGIS.

Christian,

Do the GeoTIFFs look OK in other software e.g. QGIS or OpenEV?

What GRASS version? r.out.gdal in GRASS < 6.3 is a shell
script (wrapper around gdal_translate) and works well
AFAICT. It's also present in GRASS 6.3 as r.out.gdal.sh.

But, the r.out.gdal in 6.3 is a new module written in C, and
 it has a bug about null data handling [1]. I'm not sure,
but maybe it's related.

Please try the shell script r.out.gdal version and let us
know if it works.

If neither does please provide a sample dataset and a
procedure to reproduce the error.

> I need to have them as GeoTIFFs for the easy im- and export. I am aware 
> that I can also use r.out.ascii but then I have to do an import procedure 
> in ArcGIS. For nearly 1000 images that is a bit hard to do.

As a workaround you can export with r.out.ascii and
batch-convert them into GeoTIFF with gdal_translate, eg.
given that your ascii rasters have "asc" extension:

for i in *.asc; do gdal_translate (your options go here) $i
$i.tif; done

[1]http://wald.intevation.org/tracker/?func=detail&aid=405&group_id=21&atid=204

Maciek