Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
Updated manual page: here
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=name [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=name [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 inhab >= 10000
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 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
- 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.
v.delaunay
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: 2015-01-15 00:42:19 -0800 (Thu, 15 Jan 2015) $
SOURCE CODE
Available at: v.hull source code (history)
Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
Updated manual page: here
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GRASS Development Team,
GRASS GIS 7.2.4svn Reference Manual