[GRASS-dev] Re: [GRASS GIS] #959: r.surf.contour. Resulting range of values has an incorrect 0 minimum.

[GRASS GIS]

#959: r.surf.contour. Resulting range of values has an incorrect 0 minimum.
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  Reporter:  clerici  |       Owner:  grass-dev at lists.osgeo.org
      Type:  defect   |      Status:  new                      
  Priority:  normal   |   Milestone:  6.4.0                    
 Component:  Raster   |     Version:  svn-releasebranch64      
Resolution:           |    Keywords:  r.surf.contour, NULL     
  Platform:  Linux    |         Cpu:  Unspecified              
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Changes (by hamish):

  * keywords:  => r.surf.contour, NULL
  * version:  unspecified => svn-releasebranch64

Comment:

 try "r.null dem setnull=0"

 r.surf.contour is known to treat 0 as NULL; perhaps that also works the
 other way too with NULL being treated as 0??

 a couple of subtle things to note:
  * MASK maps are only applied when reading raster map cells from the disk.
 It has no effect on writing raster maps to the disk. So a MASK map will
 have no effect on r.surf.contour which only reads vector maps.

  * r.info doesn't read raster cells, it just summarizes the raster map's
 metadata files. So MASK (or region settings) has no effect on it either.

  * r.univar and d.histogram do on the other hand read cells so do respect
 the MASK.

  * r.mapcalc works because the MASK is applied while reading the `dem` map
 from the disk.


 > This seems a very old feature as I had the same results
 > with GRASS6.5, 6.4, 6.3 and 6.2.

 The bug is even older than that.. see this bug report which I filed back
 in late 2002 (yes, it's still open!)
  http://intevation.de/rt/webrt?serial_num=1402
 and the BUGS section of the r.surf.contour help page. The module does a
 really really nice job, but it has never fully been ported from GRASS 4.x
 (pre-NULL and floating point map support).


 Hamish

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/959#comment:1>
GRASS GIS <http://grass.osgeo.org>