NAME
r.topidx - Creates topographic index, ln(a/tan(beta)), map from elevation map.
KEYWORDS
raster
SYNOPSIS
r.topidx
r.topidx help
r.topidx [-v] input=string output=string [--overwrite]
Flags:
- -v
- Output verbosely
- --overwrite
- Force overwrite of output files
Parameters:
- input=string
- Elevation map
- output=string
- Topographic index ln(a/tanB) 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: 2007/01/17 16:35:59 $
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