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

       M. de Berg, M. van Kreveld, M. Overmars, O. Schwarzkopf, (2000).  Computational  geometry,  chapter  1.1,
       2-8.  J. O'Rourke, (1998). Computational Geometry in C (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) $

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       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                       v.hull(1grass)