1r.fillnulls(1) Grass User's Manual r.fillnulls(1)
2
6 r.fillnulls - Fills no-data areas in raster maps using v.surf.rst
7 splines interpolation
8
10 raster, elevation, interpolation
11
13 r.fillnulls
14 r.fillnulls help
15 r.fillnulls input=string output=string [tension=float]
16 [smooth=float] [--overwrite]
17 Flags:
19 --overwrite
20 Parameters:
22 input=string
23 Raster map in which to fill nulls
24 output=string
26 Output raster map with nulls filled by interpolation from surround‐
27 ing values
28 tension=float
30 Spline tension parameter Default: 40.
31 smooth=float
33 Spline smoothing parameter Default: 0.1
34
36 r.fillnulls - Fills NULL (no data areas) in input map and stores
37 filled map to a new output map. The fill data are interpolated from the
38 no data area boundaries buffer using v.surf.rst spline interpolation.
39 (GRASS Shell Script)
40
42 Each area boundary buffer is set to three times the map resolution to
43 get nominally three points around the edge. This way the algorithm
44 interpolates into the hole with a trained slope and curvature at the
45 edges, in order to avoid that such a flat plane is generated in a hole.
46 During the interpolation following warning may occur:
48 Warning: strip exists with insufficient data
50 Warning: taking too long to find points for interpolation--please
51 change the region to area where your points are
52 This warning is generated if large data holes exist within the surface.
54 As the idea of r.fillnulls is to fill such holes, the user may ignore
55 the warning. The interpolation will be continued. However, the user may
56 pay attention to below notes.
57
59 The algorithm is based on v.surf.rst regularized splines with tension
60 interpolation module which interpolates the raster cell values for NULL
61 data areas from the boundary values of the NULL data area. An eventual
62 raster MASK is respected during the NULL data area(s) filling. The
63 interpolated values are patched into the NULL data area(s) of the input
64 map and saved into a new raster map.
65
67 Depending on the shape of the NULL data area(s) problems may occur due
68 to an insufficient number of input cell values for the interpolation
69 process. Most problems will occur if a NULL data area reaches a large
70 amount of the map boundary. The user will have to carefully check the
71 result using r.mapcalc (generating a difference map to the input map)
72 and/or d.what.rast to query individual cell values.
73
75 r.fill.dir, v.surf.rst
76 Mitas, L., Mitasova, H., 1999, Spatial Interpolation. In: P.Longley,
78 M.F. Goodchild, D.J. Maguire, D.W.Rhind (Eds.), Geographical Informa‐
79 tion Systems: Principles, Techniques, Management and Applications,
80 Wiley, pp.481-492
81 Mitasova H., Mitas L., Brown W.M., D.P. Gerdes, I. Kosinovsky,
83 Baker, T.1995, Modeling spatially and temporally distributed phenomena:
84 New methods and tools for GRASS GIS. International Journal of GIS, 9
85 (4), special issue on Integrating GIS and Environmental modeling,
86 433-446.
87 Mitasova H. and Mitas L. 1993: Interpolation by Regularized Spline
89 with Tension: I. Theory and Implementation, Mathematical Geology 25,
90 641-655.
91 Mitasova H. and Hofierka L. 1993: Interpolation by Regularized Spline
93 with Tension: II. Application to Terrain Modeling and Surface Geometry
94 Analysis, Mathematical Geology 25, 657-667.
95
97 r.fillnulls: Markus Neteler, University of Hannover
98 and authors of v.surf.rst
100 Improvement by Hamish Bowman, NZ
101 Last changed: $Date: 2006/04/20 21:31:24 $
103 Full index
105GRASS 6.2.2 r.fillnulls(1)