[GRASS-dev] Re: [GRASS GIS] #1088: r.fillnulls: support other interpolation methods

GRASS GIS trac at osgeo.org
Mon Jun 21 04:29:31 EDT 2010


#1088: r.fillnulls: support other interpolation methods
-------------------------+--------------------------------------------------
 Reporter:  kyngchaos    |       Owner:  grass-dev@…              
     Type:  enhancement  |      Status:  new                      
 Priority:  normal       |   Milestone:  6.5.0                    
Component:  Raster       |     Version:  svn-develbranch6         
 Keywords:  fillnulls    |    Platform:  All                      
      Cpu:  All          |  
-------------------------+--------------------------------------------------

Comment(by mmetz):

 In grass 7, it's already implemented in r.resamp.bspline. r.resamp.bspline
 interpolates a raster to the current resolution, filling NULL cells on the
 fly, or optionally only interpolates NULL
 cells. Available methods are bilinear and bicubic, tested with SRTM data,
 filling large gaps in the European Alps.

 For grass 6.x, I would use a different approach to r.fillnulls to follow
 the design of v.surf.bspline, because only interpolating NULL cells is
 already possible with v.surf.bspline:

 Create a new raster where NULL cells in the original surface raster are
 set to something else than NULL, others to NULL. Convert both raster maps
 to vector points. Use the vector points representing NULL cells as sparse
 points input for v.surf.bspline. Recommended settings for v.surf.bspline
 in this case are sie = 2 * ewres, sin = 2 * nsres, lambda = 0.005 (best in
 my tests, should be somewhere between 0.001 and 0.01). The output raster
 holds the interpolated NULL cells and can be patched with the original
 surface.

 Although all lidar tools work within the current region, none respects a
 MASK. I'm not sure how this could be implemented properly and efficiently,
 currently there will be IMHO harmless warnings about no points in the
 current subregion.

 Markus M

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/1088#comment:7>
GRASS GIS <http://grass.osgeo.org>



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