[GRASS-dev] [GRASS GIS] #1506: r.to.rast3: support for float datatype

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1

#1506: r.to.rast3: support for float datatype
-------------------------+--------------------------------------------------
Reporter: hamish | Owner: grass-dev@…
     Type: enhancement | Status: new
Priority: normal | Milestone: 6.5.0
Component: Raster3D | Version: svn-trunk
Keywords: r.to.rast3 | Platform: All
      Cpu: All |
-------------------------+--------------------------------------------------
Hi,

3D rasters can either be 'float's or 'double's. But r.to.rast3 always
creates doubles. For a 3D raster with many many cells this can be a rather
expensive problem.

thanks,
Hamish

ps- why no raster 3d support for integers? (e.g. category == geologic rock
type)

pps- why not FCELL,DCELL to match 2D rasters? or are they anachronisms
from an era when IEEE FPs were still in strong competition with IBM's FP,
etc?

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/1506&gt;
GRASS GIS <http://grass.osgeo.org>

2

#1506: r.to.rast3: support for float datatype
-------------------------+--------------------------------------------------
Reporter: hamish | Owner: grass-dev@…
     Type: enhancement | Status: new
Priority: normal | Milestone: 6.5.0
Component: Raster3D | Version: svn-trunk
Keywords: r.to.rast3 | Platform: All
      Cpu: All |
-------------------------+--------------------------------------------------

Comment(by hamish):

ps- the post-processing work-around:
{{{
  r3.mapcalc "map3d.float = float(map3d)"
}}}

unfortunately the result is many many times larger. (4.6mb double -> 86mb
float grid3/cell file in my test)

{{{
  grid3$ diff map3d/cellhd map3d.float/cellhd
  @@ -15,11 +15,11 @@
   TileDimensionX: 8
   TileDimensionY: 8
   TileDimensionZ: 8
  -CellType: double
  +CellType: float
   useCompression: 1
   useRle: 1
   useLzw: 0
  -Precision: 23
  +Precision: -1
   nofHeaderBytes: 16
   useXdr: 1
   hasIndex: 1
}}}

but there is no `r3.compress` or `r3.support` utility to adjust that. (is
precision=23 meaningful for doubles? isn't anything >16 sig. digits going
to be noise?)

Only `r3.in.ascii` and `r3.in.v5d` have controls for these:
{{{
            type Data type used in the output file
                   options: default,double,float
                   default: default
       precision Precision used in the output file (default, max, or 0 to
52)
                   default: default
     compression The compression method used in the output file
                   options: default,rle,none
                   default: default
   tiledimension The dimensions of the tiles used in the output file
                   default: default
}}}

?,
Hamish

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/1506#comment:1&gt;
GRASS GIS <http://grass.osgeo.org>