.TH r.contour 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBr.contour\fR\fR  - Produces a vector map of specified contours from a raster map.
.SH KEYWORDS
raster, DEM, contours, vector
.SH SYNOPSIS
\fBr.contour\fR
.br
\fBr.contour help\fR
.br
\fBr.contour\fR [\-\fBqn\fR] \fBinput\fR=\fIname\fR \fBoutput\fR=\fIname\fR  [\fBlevels\fR=\fIfloat\fR[,\fIfloat\fR,...]]   [\fBminlevel\fR=\fIfloat\fR]   [\fBmaxlevel\fR=\fIfloat\fR]   [\fBstep\fR=\fIfloat\fR]   [\fBcut\fR=\fIinteger\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-q\fR" 4m
.br
Run quietly
.IP "\fB\-n\fR" 4m
.br
Suppress single crossing error messages
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR" 4m
.br
Name of input raster map
.IP "\fBoutput\fR=\fIname\fR" 4m
.br
Name for output vector map
.IP "\fBlevels\fR=\fIfloat[,\fIfloat\fR,...]\fR" 4m
.br
List of contour levels
.IP "\fBminlevel\fR=\fIfloat\fR" 4m
.br
Minimum contour level
.IP "\fBmaxlevel\fR=\fIfloat\fR" 4m
.br
Maximum contour level
.IP "\fBstep\fR=\fIfloat\fR" 4m
.br
Increment between contour levels
.IP "\fBcut\fR=\fIinteger\fR" 4m
.br
Minimum number of points for a contour line (0 -> no limit)
.br
Default: \fI0\fR
.PP
.SH DESCRIPTION
\fIr.contour\fR produces a GRASS binary vector map of specified contours from a GRASS raster map.
Contours can be produced using a comma-separated list of values in \fBlevels\fR, or at some regular increment using the \fBstep\fR parameter, using \fBminlevel\fR and \fBmaxlevel\fR as minimum and maximum contour values, respectively. If no \fBminlevel\fR or \fBmaxlevel\fR is specified, the minimum and maximum cell values in the \fBinput\fR raster map will be used.
.SH NOTES
\fIr.contour\fR will either step through incremental contours or produce
contours from a list of levels, not both. If both a list of levels and
a step are specified, the list will be produced and the step will be ignored.
.PP
Zero is treated as a valid data value by \fIr.contour\fR.
.PP
If a contour level exactly matches a category value in the raster map,
the contour line may backtrack on itself, causing illegal arcs to be produced
in the output GRASS vector map.
.PP
The optional \fBcut\fR parameter allows the user to specify a minimum number of
raster cells eligilble to be included in a contour line written to the \fBoutput\fR 
vector map. It acts like a filter, omitting spurs, single points, etc., making the output more generalized.
.SH EXAMPLE
In the Spearfish location, produce a vector contour map from input raster \fIelevation.dem\fR 
with contour levels from 1000m to 2000m, 100m contour step, and a minimum of 200 input raster
points contributing to the contour line:
r.contour input=elevation.dem output=elevation_dem_contours minlevel=1000 maxlevel=2000 step=100 cut=200
.DE
\fR
.SH AUTHORS
Terry Baker, U.S. Army Construction Engineering Research Laboratory
.br
3/2001: cut parameter and fixes by Andrea Aime (aaime@libero.it)
.PP
\fILast changed: $Date: 2008-05-16 21:09:06 +0200 (Fri, 16 May 2008) $\fR
.PP
Full index
.PP
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