1v.hull(1)                     Grass User's Manual                    v.hull(1)
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NAME

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

9       vector, geometry, 3D
10

SYNOPSIS

12       v.hull
13       v.hull --help
14       v.hull  [-rf]  input=name   [layer=string]   output=name   [cats=range]
15       [where=sql_query]    [--overwrite]   [--help]   [--verbose]   [--quiet]
16       [--ui]
17
18   Flags:
19       -r
20           Limit to current region
21
22       -f
23           Create a ’flat’ 2D hull even if the input is 3D points
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25       --overwrite
26           Allow output files to overwrite existing files
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28       --help
29           Print usage summary
30
31       --verbose
32           Verbose module output
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34       --quiet
35           Quiet module output
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37       --ui
38           Force launching GUI dialog
39
40   Parameters:
41       input=name [required]
42           Name of input vector map
43           Or data source for direct OGR access
44
45       layer=string
46           Layer number or name (’-1’ for all layers)
47           A  single  vector map can be connected to multiple database tables.
48           This number determines which table to use. When  used  with  direct
49           OGR access this is the layer name.
50           Default: -1
51
52       output=name [required]
53           Name for output vector map
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55       cats=range
56           Category values
57           Example: 1,3,7-9,13
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59       where=sql_query
60           WHERE conditions of SQL statement without ’where’ keyword
61           Example: income < 1000 and population >= 10000
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DESCRIPTION

64       v.hull  computes the convex hull of a vector map and outputs the convex
65       hull polygon as a vector area map. The convex hull, or convex envelope,
66       for  an object or a set of objects is the minimal convex set containing
67       the given objects. This module creates a vector polygon containing  all
68       vector points or lines of the input map.
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70       In  the  case  of  3D input points, the hull will be a 3D hull as well,
71       unless the user specifies the -f flag. The 3D hull will be composed  of
72       triangular faces.
73       Fig: Convex hull polygon created with v.hull
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NOTES

76       In order to use the where option the layer option must be set to a pos‐
77       itive number (the default is ’-1’  for  ’all  layers’),  otherwise  all
78       points from all layers will be used and the cats and where options will
79       be ignored.
80

EXAMPLE

82       Example of v.hull 3D output (using two random 3D  point  clouds,  North
83       Carolina sample data set):
84       g.region rural_1m -p
85       r.mapcalc "zero = 0"
86       v.random -z output=random3d_a n=10 zmin=0 zmax=200
87       v.random -z output=random3d_b n=15 zmin=400 zmax=600
88       v.hull input=random3d_a output=random3d_a_hull
89       v.hull input=random3d_b output=random3d_b_hull
90       d.mon wx0
91       d.vect random3d_a_hull
92       d.vect random3d_a color=red
93       d.vect random3d_b_hull
94       d.vect random3d_b color=red
95       # 3D view in wxGUI (g.gui)
96       Fig: Convex hull in 3D from 3D points created with v.hull
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REFERENCES

99           ·   M.  de  Berg,  M.  van  Kreveld,  M.  Overmars, O. Schwarzkopf,
100               (2000). Computational geometry, chapter 1.1, 2-8.
101
102           ·   J. O’Rourke, (1998). Computational Geometry in C  (Second  Edi‐
103               tion), chapter 4.
104

SEE ALSO

106        v.delaunay
107

AUTHOR

109       Andrea Aime, Modena, Italy
110       Markus Neteler, ITC-irst (update to 5.7)
111       Benjamin Ducke, CAU Kiel (3D hull support)
112       Martin Landa, CTU in Prague, Czech Republic (vector lines support)
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114       Last changed: $Date: 2018-02-22 20:14:51 +0100 (Thu, 22 Feb 2018) $
115

SOURCE CODE

117       Available at: v.hull source code (history)
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119       Main  index  | Vector index | Topics index | Keywords index | Graphical
120       index | Full index
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122       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.0 Reference Manual
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126GRASS 7.6.0                                                          v.hull(1)
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