NAME
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 using s.surf.rst spline interpolation.
(GRASS Shell Script)
SYNOPSIS
r.fillnulls
r.fillnulls input=name output=name
OPTIONS
Parameters:
- input=name
- raster map containing NULL data area(s)/pixel(s)
- output=name
- raster map with NULL areas filled by RST interpolation
NOTES
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.
ATTENTION
The algorithm is based on s.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 r.mapcalc (generating a difference map to the
input map) and/or d.what.rast to
query individual cell values.
SEE ALSO
r.fill.dir,
s.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.
Mitasova H.
and Mitas L. 1993: Interpolation by Regularized Spline with Tension: I.
Theory and Implementation, Mathematical Geology 25, 641-655.
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.
AUTHORS
r.fillnulls: Markus Neteler, University of Hannover
and authors of s.surf.rst
Last changed: $Date: 2003/02/05 12:45:39 $