v.centroids.1grass - Man Page

Adds missing centroids to closed boundaries.


vector, centroid, area


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



Allow output files to overwrite existing files


Print usage summary


Verbose module output


Quiet module output


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


Action to be taken
Options: add
Default: add


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


Category number starting value
Default: 1


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

See Also



module: M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
help page: Trevor Wiens

Source Code

Available at: v.centroids source code (history)

Accessed: Tuesday Mar 19 11:02:39 2024

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