.TH r.topidx 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBr.topidx\fR\fR  - Creates topographic index map from elevation raster map.
.SH KEYWORDS
raster, hydrology
.SH SYNOPSIS
\fBr.topidx\fR
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\fBr.topidx help\fR
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\fBr.topidx input\fR=\fIname\fR \fBoutput\fR=\fIname\fR  [\-\-\fBoverwrite\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-\-overwrite\fR" 4m
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Allow output files to overwrite existing files
.IP "\fB\-\-verbose\fR" 4m
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Verbose module output
.IP "\fB\-\-quiet\fR" 4m
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Quiet module output
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.SS Parameters:
.IP "\fBinput\fR=\fIname\fR" 4m
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Input elevation map
.IP "\fBoutput\fR=\fIname\fR" 4m
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Output topographic index map
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.SH DESCRIPTION
\fIr.topidx\fR creates topographic index (wetness index), ln(a/tan(beta)), map from
elevation map
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where
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a: the area of the hillslope per unit contour length that drains through any point,
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tan(beta): the local surface topographic slope (delta vertical) / (delta horizontal).
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Input maps may have NULL values.  For example, if you have a MASK for
a watershed (basin map from \fIr.water.outlet\fR), the
following command will create a masked elevation map (belev):
\fC
.DS
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r.mapcalc "belev = if(isnull(basin), basin, elev)"
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.DE
\fR
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\fIr.stats -Anc\fR prints out averaged statistics for topographic index.
.SH SEE ALSO
\fIr.topmodel\fR,
\fIr.water.outlet\fR,
\fIr.mapcalc\fR
.SH 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.
.SH AUTHORS
Main algorithm sources are rewritten from GRIDATB.FOR.
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Thanks to Keith Beven.
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GRASS port by Huidae Cho
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Hydro Laboratory, Kyungpook National University, South Korea
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\fILast changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $\fR
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Full index
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© 2003-2014 GRASS Development Team