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NAME

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

KEYWORDS

raster, DEM, contours, vector

SYNOPSIS

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

Flags:

-q
Run quietly
-n
Suppress single crossing error messages
--overwrite
Allow output files to overwrite existing files
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

input=name
Name of input raster map
output=name
Name for output vector map
levels=float[,float,...]
List of contour levels
minlevel=float
Minimum contour level
maxlevel=float
Maximum contour level
step=float
Increment between contour levels
cut=integer
Minimum number of points for a contour line (0 -> no limit)
Default: 0

DESCRIPTION

r.contour 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 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 GRASS 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.

EXAMPLE

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

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: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $


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