table of contents
r.topidx(1grass) | GRASS GIS User's Manual | r.topidx(1grass) |
NAME¶
r.topidx - Creates a topographic index (wetness index) raster map from an elevation raster map.
KEYWORDS¶
raster, hydrology, wetness, topographic index
SYNOPSIS¶
r.topidx
r.topidx --help
r.topidx input=name output=name
[--overwrite] [--help] [--verbose] [--quiet]
[--ui]
Flags:¶
- --overwrite
-
Allow output files to overwrite existing files - --help
-
Print usage summary - --verbose
-
Verbose module output - --quiet
-
Quiet module output - --ui
-
Force launching GUI dialog
Parameters:¶
- input=name [required]
-
Name of input elevation raster map - output=name [required]
-
Name for output topographic index raster map
DESCRIPTION¶
r.topidx creates topographic index (wetness index), ln(a/tan(beta)), map from elevation map where
- a
-
the area of the hillslope per unit contour length that drains through any point, - tan(beta)
-
the local surface topographic slope (delta vertical) / (delta horizontal).
Input maps may have NULL values. For example, if you have a MASK
for a watershed (basin map from r.water.outlet), the following
command will create a masked elevation map (belev):
r.mapcalc "belev = if(isnull(basin), basin, elev)"
r.stats -Anc prints out averaged statistics for topographic index.
Lat/long projects are not supported. If data is not projected, please create a new project with a projected coordinate reference system and reproject the data there. Please run r.topidx from that project.
EXAMPLE¶
Running the command below will generate the topographic index map
shown in the figure:
g.region raster=elevation -p r.topidx input=elevation output=topidx_elevation
Figure: topographic index map derived from elevation map
REFERENCES¶
Cho, H., 2000. GIS Hydrological Modeling System by Using Programming Interface of GRASS. Master’s Thesis, Department of Civil Engineering, Kyungpook National University, Korea.
Moore, I.D., R.B. Grayson, and A.R. Ladson, 1991. Digital Terrain Modeling: A Review of Hydrological, Geomorphological, and Biological Applications. Hydrological Processes 5:3-30.
SEE ALSO¶
r.topmodel, r.water.outlet, r.mapcalc
Known issues
AUTHORS¶
Huidae Cho
Hydro Laboratory, Kyungpook National University, South Korea
Based on GRIDATB.FOR by Keith Beven.
SOURCE CODE¶
Available at: r.topidx source code (history)
Accessed: Thursday Aug 01 05:16:31 2024
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