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   r.fillnulls - Fills NULL (no data areas) in input map and stores filled
   map to a new output map. The fill data are interpolated from the no
   data area boundaries buffer using v.surf.rst spline interpolation.
   (GRASS Shell Script)

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   Each area boundary buffer is set to three times the map resolution to
   get nominally three points around the edge. This way the algorithm
   interpolates into the hole with a trained slope and curvature at the
   edges, in order to avoid that such a flat plane is generated in a hole.

   During the interpolation following warning may occur:

   Warning: strip exists with insufficient data
   Warning: taking too long to find points for interpolation--please
   change the region to area where your points are

   This warning is generated if large data holes exist within the surface.
   As the idea of r.fillnulls is to fill such holes, the user may ignore
   the warning. The interpolation will be continued. However, the user may
   pay attention to below notes.

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   The algorithm is based on [1]v.surf.rst regularized splines with
   tension interpolation module which interpolates the raster cell values
   for NULL data areas from the boundary values of the NULL data area. An
   eventual raster MASK is respected during the NULL data area(s) filling.
   The interpolated values are patched into the NULL data area(s) of the
   input map and saved into a new raster map.

WARNING

   Depending on the shape of the NULL data area(s) problems may occur due
   to an insufficient number of input cell values for the interpolation
   process. Most problems will occur if a NULL data area reaches a large
   amount of the map boundary. The user will have to carefully check the
   result using [2]r.mapcalc (generating a difference map to the input
   map) and/or [3]d.what.rast to query individual cell values.

СÐ. ТÐÐÐÐ

   [4]r.fill.dir, [5]v.surf.rst

   Mitas, L., Mitasova, H., 1999, Spatial Interpolation. In: P.Longley,
   M.F. Goodchild, D.J. Maguire, D.W.Rhind (Eds.), Geographical
   Information Systems: Principles, Techniques, Management and
   Applications, Wiley, pp.481-492

   Mitasova H., Mitas L.,  Brown W.M.,  D.P. Gerdes, I. Kosinovsky, Baker,
   T.1995, Modeling spatially and temporally distributed phenomena: New
   methods and tools for GRASS GIS. International Journal of GIS, 9 (4),
   special issue on Integrating GIS and Environmental modeling, 433-446.

   [6]Mitasova H. and Mitas L. 1993: Interpolation by Regularized Spline
   with Tension: I. Theory and Implementation, Mathematical Geology 25,
   641-655.

   [7]Mitasova H. and Hofierka L. 1993: Interpolation by Regularized
   Spline with Tension: II. Application to Terrain Modeling and Surface
   Geometry Analysis, Mathematical Geology 25, 657-667.

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   r.fillnulls: Markus Neteler, University of Hannover

   and authors of v.surf.rst
   Improvement by Hamish Bowman, NZ

   Last changed: $Date: 2006-04-20 16:31:24 -0500 (ЧÑ, 20 Ð°Ð¿Ñ 2006) $

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References

   1. file://localhost/root/tmp/2/fin/v.surf.rst.html
   2. file://localhost/root/tmp/2/fin/r.mapcalc.html
   3. file://localhost/root/tmp/2/fin/d.what.rast.html
   4. file://localhost/root/tmp/2/fin/r.fill.dir.html
   5. file://localhost/root/tmp/2/fin/v.surf.rst.html
   6. http://skagit.meas.ncsu.edu/~helena/gmslab/papers/lmg.rev1.ps
   7. http://skagit.meas.ncsu.edu/~helena/gmslab/papers/hmg.rev1.ps