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)

SOURCE CODE

       Available at: r.contour source code (history)

       Main index | Raster index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual