[GRASS-dev] Re: [GRASS GIS] #73: r.out.gdal tiff output does not work

[GRASS GIS]

#73: r.out.gdal tiff output does not work
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  Reporter:  helena       |       Owner:  grass-dev at lists.osgeo.org
      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              
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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]

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Ticket URL: <http://trac.osgeo.org/grass/ticket/73#comment:10>
GRASS GIS <http://grass.osgeo.org>