#73: r.out.gdal tiff output does not work --------------------------+------------------------------------------------- Reporter: helena | Owner: [email protected] Type: defect | Status: new Priority: critical | Milestone: 6.4.0 Component: Raster | Version: svn-trunk Resolution: | Keywords: r.out.gdal, tiff Platform: Unspecified | Cpu: Unspecified --------------------------+------------------------------------------------- Comment (by mmetz):
Replying to [comment:2 dylan]: > The data range as reported in ArcMap 9.2 when opening a geotiff exported from r.out.gdal is (1.17549e-038,3.40282e+038). This perfectly right insofar as this is the potential data range for float32. ArcMap does not check the actual data range when loading a new layer the first time, even when real minimum and maximum values are given in the metadata. The display of a layer gets more reasonable when choosing e.g. histogram equalization as stretch because only now ArcMap is looking at the real data range, gets real min and max values and adjusts the data visualization accordingly. ArcMap behaves like this too when opening ArcInfo ASCII grid and ESRI .hdr labeled files with float32 data (same elevation raster exported into different file formats, keeping data type float32). Maybe this is not a GeoTIFF/GRASS/GDAL bug, but ArcMap is simply not very user-friendly with data visualization? Here, GRASS is much more user-friendly, because it always knows the data range of a raster and, if no color table has been specified, automatically generates a reasonable color table, usually in color and not grayscale as ArcMap does by default... The tiff file is handled by ArcMap all right, data and georeferencing information are there, but data visualization needs to be modified by hand. > > I have noticed that when setting the files symbology, when set to a fixed number of classes (ranges) the correct data range is displayed, and the image seems to work fine. This suggests that it may be an out of range or unusual (in terms of ArcMap logic) no-data value. > > [http://casoilresource.lawr.ucdavis.edu/drupal/node/337 I have updated my notes here] -- Ticket URL: <http://trac.osgeo.org/grass/ticket/73#comment:10> GRASS GIS <http://grass.osgeo.org>
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