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NAME

       v.hull  - Produces a convex hull for a given vector map.

KEYWORDS

       vector, geometry

SYNOPSIS

       v.hull
       v.hull help
       v.hull   [-af]   input=name   output=name   [--overwrite]   [--verbose]
       [--quiet]

   Flags:
       -a
           Use all vector points (do not limit to current region)

       -f
           Create a 'flat' 2D hull even if the input is 3D points

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       input=name
           Name of input vector map
           For vector lines reads their vertices

       output=name
           Name for output vector map

DESCRIPTION

       v.hull computes the convex hull of a vector map and outputs the  convex
       hull polygon as a vector area map. The convex hull, or convex envelope,
       for an object or a set of objects is the minimal convex set  containing
       the  given objects. This module creates a vector polygon containing all
       vector points or lines of the input map.

       In the case of 3D input points, the hull will be a  3D  hull  as  well,
       unless  the user specifies the -f flag. The 3D hull will be composed of
       triangular faces.
            | Fig: Convex hull polygon created with v.hull

EXAMPLE

       Example of v.hull 3D output (using two random 3D  point  clouds,  North
       Carolina sample data set):
       g.region rural_1m -p
       r.mapcalc "zero = 0"
       v.random -z output=random3d_a n=10 zmin=0 zmax=200
       v.random -z output=random3d_b n=15 zmin=400 zmax=600
       v.hull input=random3d_a output=random3d_a_hull
       v.hull input=random3d_b output=random3d_b_hull
       nviz elevation=zero vect=random3d_a_hull,random3d_b_hull

REFERENCES

(Second Edition), chapter 4.

SEE ALSO

        v.delaunay

AUTHOR

       Andrea Aime, Modena, Italy
       Markus Neteler, ITC-irst (update to 5.7)
       Benjamin Ducke, CAU Kiel (3D hull support)
       Martin Landa, CTU in Prague, Czech Republic (vector lines support)

       Last changed: $Date: 2013-04-14 01:55:49 -0700 (Sun, 14 Apr 2013) $

       Full index

       © 2003-2013 GRASS Development Team



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