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NAME

       r.contour  - Produces a vector map of specified contours from a raster map.

KEYWORDS

       raster, surface, contours, vector

SYNOPSIS

       r.contour
       r.contour --help
       r.contour   [-t]   input=name   output=name    [step=float]     [levels=float[,float,...]]
       [minlevel=float]   [maxlevel=float]   [cut=integer]   [--overwrite]  [--help]  [--verbose]
       [--quiet]  [--ui]

   Flags:
       -t
           Do not create attribute table

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input raster map

       output=name [required]
           Name for output vector map

       step=float
           Increment between contour levels

       levels=float[,float,...]
           List of contour levels

       minlevel=float
           Minimum contour level

       maxlevel=float
           Maximum contour level

       cut=integer
           Minimum number of points for a contour line (0 -> no limit)
           Default: 2

DESCRIPTION

       r.contour produces a vector map of specified contours from input raster map.  Contours can
       be produced using a comma-separated list of values in levels, or at some regular increment
       using  the  step  parameter,  using  minlevel  and maxlevel as minimum and maximum contour
       values, respectively. If no minlevel or maxlevel is specified,  the  minimum  and  maximum
       cell values in the input raster map will be used.

NOTES

       r.contour 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.

       Zero is treated as a valid data value by r.contour.

       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.

       The optional cut parameter allows the user to specify a minimum  number  of  raster  cells
       eligilble  to be included in a contour line written to the output vector map. It acts like
       a filter, omitting spurs, single points, etc., making the output more generalized.

EXAMPLES

       In the Spearfish location, produce a vector contour map from  input  raster  elevation.dem
       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

       For an example of using levels with r.contour this example uses the elevation map from the
       North Carolina database:
       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
       Contour lines shown on shaded terrain map

       For  an  example  of  using  steps with r.contour this example uses the LiDAR data derived
       elevation map from the North Carolina database:
       g.region raster=elev_lid792_1m -p
       r.contour input=elev_lid792_1m output=elev_lid792_1m_contours \
                 minlevel=100 maxlevel=150 step=10

AUTHORS

       Terry Baker, U.S. Army Construction Engineering Research Laboratory
       3/2001: cut parameter and fixes by Andrea Aime (aaime@libero.it)

       Last changed: $Date: 2016-12-09 19:14:52 +0100 (Fri, 09 Dec 2016) $

SOURCE CODE

       Available at: r.contour source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual