
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, 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
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: 2006/08/22 20:11:07 $
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