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v.centroids(1) Grass User's Manual v.centroids(1)

v.centroids - Adds missing centroids to closed boundaries.

vector, centroid, area

v.centroids
 
v.centroids --help
 
v.centroids input=name output=name [option= string] [layer=string] [cat=integer] [ step=integer] [--overwrite] [-- help] [--verbose] [--quiet] [--ui]

--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

input=name [required]
 
Name of input vector map
 
Or data source for direct OGR access
output=name [required]
 
Name for output vector map
option=string
 
Action to be taken
 
Options: add
 
Default: add
layer=string
 
Layer number or name
 
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
 
Default: 1
cat=integer
 
Category number starting value
 
Default: 1
step=integer
 
Category increment
 
Default: 1

GRASS defines vector areas as composite entities consisting of a set of closed boundaries and a centroid. The attribute information associated with that area is linked to the centroid. The v.centroids module adds centroids to closed boundaries in the input file and assigns a category number to them. The starting value as well as the increment size may be set using optional parameters.
Multiple attributes may be linked to a single vector entity through numbered fields referred to as layers. Refer to v.category for more details, as v.centroids is simply a frontend to that module.
The boundary itself is often stored without any category reference as it can mark the border between two adjacent areas. Thus it would be ambiguous as to which feature the attribute would belong. In some cases it may, for example, represent a road between two parcels of land. In this case it is entirely appropriate for the boundary to contain category information.

Create an area from a closed line using North Carolina sample dataset:
 
v.type input=busroute11 output=busroute11_boundary from_type=line to_type=boundary
v.centroids input=busroute11_boundary output=busroute11_area
 
Figure: Creating area from closed line

v.category

module: M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
 
help page: Trevor Wiens
Last changed: $Date: 2017-11-11 19:59:24 +0100 (Sat, 11 Nov 2017) $

Available at: v.centroids source code (history)
Main index | Vector index | Topics index | Keywords index | Graphical index | Full index
© 2003-2018 GRASS Development Team, GRASS GIS 7.4.3 Reference Manual
GRASS 7.4.3

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