On Thursday 28 February 2008, Patton, Eric wrote: > >can you zoom a little bit so that the region is smaller than the raster > >and then export with r.out.gdal to see whether it is still black? > >Are you also getting warning about nulls in the data even if there > >are none? > >I think there is a bug in the program (and it also does not let you set > >the number of decimal digits so it produces numbers with large number > >of digits that are useless). > > > >thanks, Helena > > Helena, > > Zooming in to a smaller region than the raster doesn't change the results. > I do get warnings about nulls, but it seems to make sense given the shape > of the data I'm working with relative to the region. > > I exported a series of tiffs using r.out.gdal today, using type=Byte and > type=UInt16. ArcGIS 9.2 was able to load the UInt16 tiffs, although very, > very slowly. The elevation.10m raster from Spearfish took about 2 minutes > to load, and it was only 5.6MB in size. The long loading time was due to > the enormous size of the color table: 65,536 (2^16) colors. I can't imagine > how long it would take Arc to load a 200MB tiff with this many colors. It > would probably crash. > > All of the Byte tiffs were red. A look at the color table in Arc showed > that all of the 255 colors were a repeating pattern of white-to-red (i.e., > 0-31, 32-63, etc.), with no green or blue colors. > > I've never had a problem with the output from r.out.tiff, using it for 6 > years now. I can view these tiffs in every image viewer and GIS on both > Linux and Windows. I imagine the reason for this is the relatively > simplified color tables in r.out.tiff tiffs? I would be great if there was > a way to get georeferencing information installed in the headers of tiffs > created from r.out.tiff. The output from r.out.gdal seems to be either way > too detailed, or not mapped properly into a 255 color space. > > Has anyone had success using the type=Byte in r.out.gdal to get > consistently good output for use in other GIS? >
I ran into some of these problems a while back and posted [1] some thoughts on the matter. I updated the linked page today with an example using SVN GRASS and ArcMap 9.2. In summary: - r.out.gdal never worked for me (or rather the resulting file would not open in ArcMap) - r.out.arc always worked, but file size problems can arise due to the ASCII nature of the output file. also the output file lacks spatial reference system data. 1. http://casoilresource.lawr.ucdavis.edu/drupal/node/337 -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
