1r.resamp.rst(1) GRASS GIS User's Manual r.resamp.rst(1)
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6 r.resamp.rst - Reinterpolates and optionally computes topographic
7 analysis from input raster map to a new raster map (possibly with dif‐
8 ferent resolution) using regularized spline with tension and smoothing.
9
11 raster, resample, splines, RST
12
14 r.resamp.rst
15 r.resamp.rst --help
16 r.resamp.rst [-td] input=name ew_res=float ns_res=float [eleva‐
17 tion=name] [slope=name] [aspect=name] [pcurvature=name] [tcur‐
18 vature=name] [mcurvature=name] [smooth=name] [maskmap=name]
19 [overlap=integer] [zscale=float] [tension=float] [theta=float]
20 [scalex=float] [--overwrite] [--help] [--verbose] [--quiet]
21 [--ui]
22 Flags:
24 -t
25 Use dnorm independent tension
26 -d
28 Output partial derivatives instead of topographic parameters
29 --overwrite
31 Allow output files to overwrite existing files
32 --help
34 Print usage summary
35 --verbose
37 Verbose module output
38 --quiet
40 Quiet module output
41 --ui
43 Force launching GUI dialog
44 Parameters:
46 input=name [required]
47 Name of input raster map
48 ew_res=float [required]
50 Desired east-west resolution
51 ns_res=float [required]
53 Desired north-south resolution
54 elevation=name
56 Name for output elevation raster map
57 slope=name
59 Name for output slope map (or fx)
60 aspect=name
62 Name for output aspect map (or fy)
63 pcurvature=name
65 Name for output profile curvature map (or fxx)
66 tcurvature=name
68 Name for output tangential curvature map (or fyy)
69 mcurvature=name
71 Name for output mean curvature map (or fxy)
72 smooth=name
74 Name of input raster map containing smoothing
75 maskmap=name
77 Name of input raster map to be used as mask
78 overlap=integer
80 Rows/columns overlap for segmentation
81 Default: 3
82 zscale=float
84 Multiplier for z-values
85 Default: 1.0
86 tension=float
88 Spline tension value
89 Default: 40.
90 theta=float
92 Anisotropy angle (in degrees counterclockwise from East)
93 scalex=float
95 Anisotropy scaling factor
96
98 r.resamp.rst reinterpolates the values a from given raster map (named
99 input) to a new raster map (named elev). This module is intended for
100 reinterpolation of continuous data to a different resolution rather
101 than for interpolation from scattered data (use the v.surf.* modules
102 for that purpose).
103 The extent of all resulting raster maps is taken from the settings of
105 the actual computational region (which may differ from the extent of
106 the input raster map). The resolution of the computational region how‐
107 ever has to be aligned to the resolution of the input map to avoid
108 artefacts.
109 Reinterpolation (resampling) is done to higher, same or lower resolu‐
111 tion specified by the ew_res and ns_res parameters.
112 All resulting raster maps are created using the settings of the current
114 region (which may be different from that of the input raster map).
115 Optionally, and simultaneously with interpolation, topographic parame‐
117 ters are computed from an input raster map containing z-values of ele‐
118 vation/depth: slope, aspect, profile curvature (measured in the direc‐
119 tion of steepest slope), tangential curvature (measured in the direc‐
120 tion of a tangent to contour line) and/or mean curvature are computed
121 from and saved as raster maps as specified by the options slope,
122 aspect, pcurv, tcurv, mcurv respectively.
123 If the -d flag is set the program outputs partial derivatives fx, fy,
125 fxx, fxy, and fyy instead of slope, aspect and curvatures.
126 For noisy data it is possible to define spatially variable smoothing by
128 providing a raster map named by the smooth option containing smoothing
129 parameters. With the smoothing parameter set to zero (smooth is not
130 given or contains zero data), the resulting surface passes exactly
131 through the data points.
132 The user can also define a raster map (named with maskmap) which will
134 be used as a mask. The interpolation is skipped for cells which have
135 zero or NULL value in the mask.
136 Zero values will be assigned to these cells in all output raster maps.
138 The zmult parameter allows the user to rescale the z-values which may
140 be useful, e.g., for transformation of elevations given in feet to
141 meters, so that the proper values of slopes and curvatures can be com‐
142 puted. The default value is 1.
143 A regularized spline with tension method is used for the interpolation.
145 The tension parameter tunes the character of the resulting surface from
146 thin plate to membrane. Higher values of tension parameter reduce the
147 overshoots that can appear in surfaces with rapid change of gradient.
148 The -t flag can be set to use "dnorm independent tension".
150 The interpolation is performed for overlapping rectangular segments.
152 The user can define the width of overlap (in number of cells) with the
153 overlap option. The default value is 3.
154
156 r.resamp.rst uses regularized spline with tension for interpolation (as
157 described in Mitasova and Mitas, 1993).
158 The region is temporarily changed while writing output files with
160 desired resolution. Topographic parameters are computed in the same way
161 as in the v.surf.rst module. (See also Mitasova and Hofierka, 1993)
162 The raster map used with the smooth option should contain variable
164 smoothing parameters. These can be derived from errors, slope, etc.
165 using the r.mapcalc module.
166 The program gives warning when significant overshoots appear and higher
168 tension should be used. However, with tension set too high the result‐
169 ing surface changes its behavior to a membrane (rubber sheet stretched
170 over the data points resulting in a peak or pit in each given point and
171 everywhere else the surface goes rapidly to trend). Smoothing can be
172 used to reduce the overshoots. When overshoots occur the resulting elev
173 file will have white color in the locations of overshoots since the
174 color table for the output file is the same as colortable for raster
175 input file.
176 The program checks the numerical stability of the algorithm by computa‐
178 tion of values at given points, and prints the maximum difference found
179 into the history file of raster map elev (view with r.info). An
180 increase in tension is suggested if the difference is unacceptable.
181 For computations with smoothing set to 0 this difference should be 0.
182 With a smoothing parameter greater than zero the surface will not pass
183 through the data points exactly, and the higher the parameter the
184 closer the surface will be to the trend.
185 The program writes the values of parameters used in computation into
187 the comment part of the elev map history file. Additionally the follow‐
188 ing values are also written to assist in the evaluation of results and
189 choosing of suitable parameters:
190 · minimum and maximum z values in the data file (zmin_data,
192 zmax_data) and in the interpolated raster map (zmin_int,
193 zmax_int),
194 · maximum difference between the given and interpolated z value
196 at a given point (errtotal),
197 · rescaling parameter used for normalization (dnorm), which
199 influences the tension.
200 The program gives a warning when the user wants to interpolate outside
202 the region given by the input raster map’s header data. Zooming into
203 the area where the points are is suggested in this case.
204 When a mask is used, the program uses all points in the given region
206 for interpolation, including those in the area which is masked out, to
207 ensure proper interpolation along the border of the mask. It therefore
208 does not mask out the data points; if this is desirable, it must be
209 done outside r.resamp.rst before processing.
210
212 Resampling the Spearfish 30m resolution elevation model to 15m:
213 # set computation region to original map (30m)
214 g.region raster=elevation.dem -p
215 # resample to 15m
216 r.resamp.rst input=elevation.dem ew_res=15 ns_res=15 elevation=elev15
217 # set computation region to resulting map
218 g.region raster=elev15 -p
219 # verify
220 r.univar elev15 -g
221
223 g.region, r.info, r.resample, r.mapcalc, r.surf.contour, v.surf.rst
224 Overview: Interpolation and Resampling in GRASS GIS
226
228 Original version of program (in FORTRAN):
229 Lubos Mitas, NCSA, University of Illinois at Urbana Champaign, Il
230 Helena Mitasova, US Army CERL, Champaign, IllinoisÂ
231 Modified program (translated to C, adapted for GRASS , segmentation
233 procedure):
234 Irina Kosinovsky, US Army CERL.
235 Dave Gerdes, US Army CERL.
236
238 Mitas, L., Mitasova, H., 1999, Spatial Interpolation. In: P.Longley,
239 M.F. Goodchild, D.J. Maguire, D.W.Rhind (Eds.), Geographical Informa‐
240 tion Systems: Principles, Techniques, Management and Applications,
241 Wiley, 481-492.
242 Mitasova, H. and Mitas, L., 1993. Interpolation by regularized spline
244 with tension: I. Theory and implementation, Mathematical Geology No.25
245 p.641-656.
246 Mitasova, H. and Hofierka, L., 1993. Interpolation by regularized
248 spline with tension: II. Application to terrain modeling and surface
249 geometry analysis, Mathematical Geology No.25 p.657-667.
250 Talmi, A. and Gilat, G., 1977. Method for smooth approximation of data,
252 Journal of Computational Physics , 23, pp 93-123.
253 Wahba, G., 1990. Spline models for observational data, CNMS-NSF
255 Regional Conference series in applied mathematics, 59, SIAM, Philadel‐
256 phia, Pennsylvania.
257
259 Available at: r.resamp.rst source code (history)
260 Main index | Raster index | Topics index | Keywords index | Graphical
262 index | Full index
263 © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
265GRASS 7.8.5 r.resamp.rst(1)