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NAME
r.topidx - Creates topographic index map from elevation raster map.
KEYWORDS
raster, hydrology
SYNOPSIS
r.topidx
r.topidx help
r.topidx input=name output=name [--overwrite] [--verbose] [--quiet]
Flags:
- --overwrite
- Allow output files to overwrite existing files
- --verbose
- Verbose module output
- --quiet
- Quiet module output
Parameters:
- input=name
- Input elevation map
- output=name
- Output topographic index 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.
SEE ALSO
r.topmodel,
r.water.outlet,
r.mapcalc
REFERENCE
Moore, I.D., R.B. Grayson, and A.R. Ladson, 1991. Digital terrain
modeling: A review of hydrological, geomorphological, and biological
applications. Hydrol. Processes 5:3-30.
AUTHORS
Main algorithm sources are rewritten from GRIDATB.FOR.
Thanks to Keith Beven.
GRASS port by Huidae Cho
Hydro Laboratory, Kyungpook National University, South Korea
Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $
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