On Fri, Jul 24, 2009 at 5:44 PM, Frank Warmerdam<[email protected]> wrote: > Rainer M Krug wrote: >> >> Hi >> >> I have a geotiff and want to use gdalwarp to warp to it into a >> different projection. >> I do the following: >> >> gdalwarp -s_srs EPSG:32734 -t_srs '+proj=longlat +ellps=WGS84 >> +no_defs' Outeniqua.tiff Outeniqua_wgs84.tiff >> >> The problem is, that in Outeniqua_wgs84.tiff, the nodata values from >> Outeniqua.tiff become translated into -9999. In addition, the areas >> new to Outeniqua_wgs84.tiff (due to the warping) become 1. >> >> Which options do I have to use to keep the nodata values and to make >> the values of the "new areas" also as nodata values? > > Rainer, > > I believe you want to pass the warp option INIT_DEST=-9999 to set all pixels > that do not come from the source file to -9999.
Thanks a lot - that solved it partly. I now have all original pixels unequal to NULL now warped as they should be. Only slight problemk now: all NULL values from the input file, are now -9999 and I would prefer to heve them as NULL. I managed that by using gdal_translate and the -a_nulldata option, but shouldn't that be possible in gralwarp? Rainer > > This is done with the -wo flag to gdalwarp. > > eg. > > gdalwarp -wo INIT_DEST=-9999 ... > > The avalilable warp options are described in a web page available linked off > the gdalwarp utility page. > > Best regards, > -- > ---------------------------------------+-------------------------------------- > I set the clouds in motion - turn up | Frank Warmerdam, > [email protected] > light and sound - activate the windows | http://pobox.com/~warmerdam > and watch the world go round - Rush | Geospatial Programmer for Rent > > -- Rainer M. Krug, Centre of Excellence for Invasion Biology, Stellenbosch University, South Africa _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
