1r.resamp.rst(1) Grass User's Manual r.resamp.rst(1)
2
6 r.resamp.rst - Reinterpolates and computes topographic analysis from
7 input raster file to a new raster file (possibly with different resolu‐
8 tion) using regularized spline with tension and smoothing.
9
11 raster
12
14 r.resamp.rst
15 r.resamp.rst help
16 r.resamp.rst [-dt] input=string ew_res=float ns_res=float
17 [elev=string] [slope=string] [aspect=string] [pcurv=string]
18 [tcurv=string] [mcurv=string] [smooth=string] [maskmap=string]
19 [overlap=integer] [zmult=float] [tension=float] [theta=float]
20 [scalex=float] [--overwrite]
21 Flags:
23 -d Output partial derivatives instead
24 -t Use dnorm independent tension
26 --overwrite
28 Parameters:
30 input=string
31 Name of the input raster file
32 ew_res=float
34 Desired east-west resolution
35 ns_res=float
37 Desired north-south resolution
38 elev=string
40 Output z-file (elevation) map
41 slope=string
43 Output slope map (or fx)
44 aspect=string
46 Output aspect map (or fy)
47 pcurv=string
49 Output profile curvature map (or fxx)
50 tcurv=string
52 Output tangential curvature map (or fyy)
53 mcurv=string
55 Output mean curvature map (or fxy)
56 smooth=string
58 Name of raster map containing smoothing
59 maskmap=string
61 Name of raster map to be used as mask
62 overlap=integer
64 Rows/columns overlap for segmentation Default: 3
65 zmult=float
67 Multiplier for z-values Default: 1.0
68 tension=float
70 Spline tension value Default: 40.
71 theta=float
73 Anisotropy angle (in degrees)
74 scalex=float
76 Anisotropy scaling factor
77
79 r.resamp.rst reinterpolates the values a from given raster file (named
80 input) to a new raster file (named elev). Reinterpolation (resampling)
81 is done to higher, same or lower resolution specified by the ew_res and
82 ns_res parameters.
83 All resulting raster files are created using the settings of the cur‐
85 rent region (which may be different from that of the input raster
86 file).
87 Optionally, and simultaneously with interpolation, the topographic
89 parameters slope, aspect, profile curvature (measured in the direction
90 of steepest slope), tangential curvature (measured in the direction of
91 a tangent to contour line) and/or mean curvature are computed and saved
92 as raster files as specified by the options slope, aspect, pcurv,
93 tcurv, mcurv respectively.
94 If the -d flag is set the program outputs partial derivatives fx, fy,
96 fxx, fxy, and fyy instead of slope, aspect and curvatures.
97 For noisy data it is possible to define spatially variable smoothing by
99 providing a raster map named by the smooth option containing smoothing
100 parameters. With the smoothing parameter set to zero (smooth is not
101 given or contains zero data), the resulting surface passes exactly
102 through the data points.
103 The user can also define a raster map (named with maskmap) which will
105 be used as a mask. The interpolation is skipped for cells which have
106 zero or NULL value in the mask.
107 Zero values will be assigned to these cells in all output raster files.
109 The zmult parameter allows the user to rescale the z-values which may
111 be useful, e.g., for transformation of elevations given in feet to
112 meters, so that the proper values of slopes and curvatures can be com‐
113 puted. The default value is 1.
114 A regularized spline with tension method is used for the interpolation.
116 The tension parameter tunes the character of the resulting surface from
117 thin plate to membrane. Higher values of tension parameter reduce the
118 overshoots that can appear in surfaces with rapid change of gradient.
119 The -t flag can be set to use "dnorm independent tension".
121 The interpolation is performed for overlapping rectangular segments.
123 The user can define the width of overlap (in number of cells) with the
124 overlap option. The default value is 3.
125
127 r.resamp.rst uses regularized spline with tension for interpolation (as
128 described in Mitasova and Mitas, 1993).
129 The region is temporarily changed while writing output files with
131 desired resolution. Topographic parameters are computed in the same way
132 as in the v.surf.rst module. (See also Mitasova and Hofierka, 1993)
133 The raster map used with the smooth option should contain variable
135 smoothing parameters. These can be derived from errors, slope, etc.
136 using the r.mapcalc module.
137 The program gives warning when significant overshoots appear and higher
139 tension should be used. However, with tension set too high the result‐
140 ing surface changes its behavior to a membrane (rubber sheet stretched
141 over the data points resulting in a peak or pit in each given point and
142 everywhere else the surface goes rapidly to trend). Smoothing can be
143 used to reduce the overshoots. When overshoots occur the resulting elev
144 file will have white color in the locations of overshoots since the
145 color table for the output file is the same as colortable for raster
146 input file.
147 The program checks the numerical stability of the algorithm by computa‐
149 tion of values at given points, and prints the maximum difference found
150 into the history file of raster map elev (view with r.info). An
151 increase in tension is suggested if the difference is unacceptable.
152 For computations with smoothing set to 0 this difference should be 0.
153 With a smoothing parameter greater than zero the surface will not pass
154 through the data points exactly, and the higher the parameter the
155 closer the surface will be to the trend.
156 The program writes the values of parameters used in computation into
158 the comment part of the elev map history file. Additionally the follow‐
159 ing values are also written to assist in the evaluation of results and
160 choosing of suitable parameters:
161 minimum and maximum z values in the data file (zmin_data,
163 zmax_data) and in the interpolated raster map (zmin_int,
164 zmax_int),
165 maximum difference between the given and interpolated z
167 value at a given point (errtotal),
168 rescaling parameter used for normalization (dnorm), which
170 influences the tension.
171 The program gives a warning when the user wants to interpolate outside
173 the region given by the input raster map's header data. Zooming into
174 the area where the points are is suggested in this case.
175 When a mask is used, the program uses all points in the given region
177 for interpolation, including those in the area which is masked out, to
178 ensure proper interpolation along the border of the mask. It therefore
179 does not mask out the data points; if this is desirable, it must be
180 done outside r.resamp.rst before processing.
181
183 g.region, r.info, r.resample, r.mapcalc, r.surf.contour, v.surf.rst
184
186 Original version of program (in FORTRAN):
187 Lubos Mitas, NCSA, University of Illinois at Urbana Champaign, Il
188 Helena Mitasova, US Army CERL, Champaign, Illinois
189 Modified program (translated to C, adapted for GRASS , segmentation
191 procedure):
192 Irina Kosinovsky, US Army CERL.
193 Dave Gerdes, US Army CERL.
194
196 Mitas, L., Mitasova, H., 1999, Spatial Interpolation. In: P.Longley,
197 M.F. Goodchild, D.J. Maguire, D.W.Rhind (Eds.), Geographical Informa‐
198 tion Systems: Principles, Techniques, Management and Applications,
199 Wiley, 481-492.
200 Mitasova, H. and Mitas, L., 1993. Interpolation by regularized spline
202 with tension: I. Theory and implementation, Mathematical Geology No.25
203 p.641-656.
204 Mitasova, H. and Hofierka, L., 1993. Interpolation by regularized
206 spline with tension: II. Application to terrain modeling and surface
207 geometry analysis, Mathematical Geology No.25 p.657-667.
208 Talmi, A. and Gilat, G., 1977. Method for smooth approximation of data,
210 Journal of Computational Physics , 23, pp 93-123.
211 Wahba, G., 1990. Spline models for observational data, CNMS-NSF
213 Regional Conference series in applied mathematics, 59, SIAM, Philadel‐
214 phia, Pennsylvania.
215 Last changed: $Date: 2005/11/12 11:48:47 $
217 Full index
219GRASS 6.2.2 r.resamp.rst(1)