.TH r.contour 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBr.contour\fR\fR  \- Produces a vector map of specified contours from a raster map.
.SH KEYWORDS
raster, surface, contours, vector
.SH SYNOPSIS
\fBr.contour\fR
.br
\fBr.contour \-\-help\fR
.br
\fBr.contour\fR [\-\fBt\fR] \fBinput\fR=\fIname\fR \fBoutput\fR=\fIname\fR  [\fBstep\fR=\fIfloat\fR]   [\fBlevels\fR=\fIfloat\fR[,\fIfloat\fR,...]]   [\fBminlevel\fR=\fIfloat\fR]   [\fBmaxlevel\fR=\fIfloat\fR]   [\fBcut\fR=\fIinteger\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-t\fR" 4m
.br
Do not create attribute table
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name of input raster map
.IP "\fBoutput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output vector map
.IP "\fBstep\fR=\fIfloat\fR" 4m
.br
Increment between contour levels
.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 "\fBcut\fR=\fIinteger\fR" 4m
.br
Minimum number of points for a contour line (0 \-> no limit)
.br
Default: \fI2\fR
.SH DESCRIPTION
\fIr.contour\fR produces a vector map of specified contours from input 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 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 EXAMPLES
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:
.br
.nf
\fC
r.contour input=elevation.dem output=elevation_dem_contours \(rs
          minlevel=1000 maxlevel=2000 step=100 cut=200
\fR
.fi
.PP
For an example of using levels with \fIr.contour\fR this example uses
the elevation map from the North Carolina database:
.br
.nf
\fC
g.region raster=elevation
r.contour in=elevation out=contours levels=60,90,120,150 \-\-o
d.mon wx0
d.rast elevation_shade
d.vect contours color=red
\fR
.fi
.br
\fIContour lines shown on shaded terrain map\fR
.PP
For an example of using steps with \fIr.contour\fR this example uses
the LiDAR data derived elevation map from the North Carolina database:
.br
.nf
\fC
g.region raster=elev_lid792_1m \-p
r.contour input=elev_lid792_1m output=elev_lid792_1m_contours \(rs
          minlevel=100 maxlevel=150 step=10
\fR
.fi
.SH AUTHORS
Terry Baker, U.S. Army Construction Engineering Research Laboratory
.br
3/2001: cut parameter and fixes by Andrea Aime (aaime@libero.it)
.SH SOURCE CODE
.PP
Available at: r.contour source code (history)
.PP
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.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual