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) $

       Full index

       © 2003-2013 GRASS Development Team