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


       raster, surface, contours, vector


       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]

           Do not create attribute table

           Allow output files to overwrite existing files

           Print usage summary

           Verbose module output

           Quiet module output

           Force launching GUI dialog

       input=name [required]
           Name of input raster map

       output=name [required]
           Name for output vector map

           Increment between contour levels

           List of contour levels

           Minimum contour level

           Maximum contour level

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


       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.


       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.


       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


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

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


       Available at: r.contour source code (history)

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