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v.hull(1)		    GRASS GIS User's Manual		     v.hull(1)

NAME
       v.hull  - Produces a 2D/3D convex hull for a given vector map.

KEYWORDS
       vector, geometry, 3D

SYNOPSIS
       v.hull
       v.hull --help
       v.hull  [-rf]  input=name   [layer=string]   output=name	  [cats=range]
       [where=sql_query]    [--overwrite]   [--help]   [--verbose]   [--quiet]
       [--ui]

   Flags:
       -r
	   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

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       input=nameA [required]
	   Name	of input vector	map
	   Or data source for direct OGR access

       layer=string
	   Layer number	or name	('-1' for all layers)
	   A  single  vector map can be	connected to multiple database tables.
	   This	number determines which	table to use. When  used  with	direct
	   OGR access this is the layer	name.
	   Default: -1

       output=nameA [required]
	   Name	for output vector map

       cats=range
	   Category values
	   Example: 1,3,7-9,13

       where=sql_query
	   WHERE conditions of SQL statement without 'where' keyword
	   Example: income < 1000 and population >= 10000

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, un-
       less the	user specifies the -f flag. The	3D hull	will  be  composed  of
       triangular faces.
       Fig: Convex hull	polygon	created	with v.hull

NOTES
       In order	to use the where option	the layer option must be set to	a pos-
       itive number (the default is '-1'  for  'all  layers'),	otherwise  all
       points from all layers will be used and the cats	and where options will
       be ignored.

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
       d.mon wx0
       d.vect random3d_a_hull
       d.vect random3d_a color=red
       d.vect random3d_b_hull
       d.vect random3d_b color=red
       # 3D view in wxGUI (g.gui)
       Fig: Convex hull	in 3D from 3D points created with v.hull

REFERENCES
	   o   M.  de  Berg,  M.  van  Kreveld,	 M.  Overmars, O. Schwarzkopf,
	       (2000). Computational geometry, chapter 1.1, 2-8.

	   o   J. O'Rourke, (1998). Computational Geometry in C	 (Second  Edi-
	       tion), 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)

SOURCE CODE
       Available at: v.hull source code	(history)

       Main  index  | Vector index | Topics index | Keywords index | Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.5 Reference	Manual

GRASS 7.8.5							     v.hull(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLE | REFERENCES | SEE ALSO | AUTHOR | SOURCE CODE

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