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 12:29:50 +0100 (Tue, 08 Nov 2011) $
Full index
© 2003-2014 GRASS Development Team
