1r.topidx(1) Grass User's Manual r.topidx(1)
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6 r.topidx - Creates a topographic index (wetness index) raster map from
7 an elevation raster map.
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10 raster, hydrology, wetness, topographic index
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13 r.topidx
14 r.topidx --help
15 r.topidx input=name output=name [--overwrite] [--help] [--verbose]
16 [--quiet] [--ui]
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18 Flags:
19 --overwrite
20 Allow output files to overwrite existing files
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22 --help
23 Print usage summary
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25 --verbose
26 Verbose module output
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28 --quiet
29 Quiet module output
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31 --ui
32 Force launching GUI dialog
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34 Parameters:
35 input=name [required]
36 Name of input elevation raster map
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38 output=name [required]
39 Name for output topographic index raster map
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42 r.topidx creates topographic index (wetness index), ln(a/tan(beta)),
43 map from elevation map
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45 where
46 a: the area of the hillslope per unit contour length that drains
47 through any point,
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49 tan(beta): the local surface topographic slope (delta vertical) /
50 (delta horizontal).
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52 Input maps may have NULL values. For example, if you have a MASK for a
53 watershed (basin map from r.water.outlet), the following command will
54 create a masked elevation map (belev):
55 r.mapcalc "belev = if(isnull(basin), basin, elev)"
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57 r.stats -Anc prints out averaged statistics for topographic index.
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60 Running the command below will generate the topographic index map shown
61 in the figure:
62 g.region raster=elevation -p
63 r.topidx input=elevation output=topidx_elevation
64 Figure: topographic index map derived from elevation map
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67 r.topmodel, r.water.outlet, r.mapcalc
68 Known issues
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71 Cho, H., 2000. GIS Hydrological Modeling System by Using Programming
72 Interface of GRASS. Master’s Thesis, Department of Civil Engineering,
73 Kyungpook National University, Korea.
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75 Moore, I.D., R.B. Grayson, and A.R. Ladson, 1991. Digital Terrain Mod‐
76 eling: A Review of Hydrological, Geomorphological, and Biological
77 Applications. Hydrological Processes 5:3-30.
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80 Huidae Cho
81 Hydro Laboratory, Kyungpook National University, South Korea
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83 Based on GRIDATB.FOR by Keith Beven.
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85 Last changed: $Date: 2017-12-19 23:54:34 +0100 (Tue, 19 Dec 2017) $
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88 Available at: r.topidx source code (history)
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90 Main index | Raster index | Topics index | Keywords index | Graphical
91 index | Full index
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93 © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
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97GRASS 7.4.4 r.topidx(1)