[GRASS-user] Closed Areas

pipppoo pipppoo at gmail.com
Mon Nov 29 05:07:24 EST 2010


Hi,

i transformed my lines into boundaries (v.type) and added than centroids
(v.centroids) to make areas out of them.

GRASS 6.4.0RC5+39438 (BMN):~ > v.type input=FNF output=FNFType
type=line,boundary --overwrite
WARNING: Vector map <FNFType> already exists and will be overwritten
Building topology for vector map <FNFType>...
Registering primitives...
597 primitives registered
1035130 vertices registered
Building areas...
 100%
597 areas built
597 isles built
Attaching islands...
 100%
Attaching centroids...
 100%
Number of nodes: 597
Number of primitives: 597
Number of points: 0
Number of lines: 0
Number of boundaries: 597
Number of centroids: 0
Number of areas: 597
Number of isles: 597
Number of areas without centroid: 597

GRASS 6.4.0RC5+39438 (BMN):~ > v.centroids input=FNFType output=FNFTypeCent
Processing features...
597 new centroids placed in output map
Copying attribute table(s)...
Building topology for vector map <FNFTypeCent>...
Registering primitives...
1194 primitives registered
1035727 vertices registered
Building areas...
 100%
597 areas built
597 isles built
Attaching islands...
 100%
Attaching centroids...
 100%
Number of nodes: 1194
Number of primitives: 1194
Number of points: 0
Number of lines: 0
Number of boundaries: 597
Number of centroids: 597
Number of areas: 597
Number of isles: 597
Number of duplicate centroids: 116
Number of areas without centroid: 116
v.category complete. 597 features modified.

The output says that to 116 areas a centroid can't be added.
Thus i controlled with v.digit, if the boundaries are closed:
http://osgeo-org.1803224.n2.nabble.com/file/n5783822/Screenshot-v.digit_-_FNF%40PERMANENT.png 

How you can see, there are just green crosses, that means that every
boundary should be closed? Or not?
But why then there are 116 areas without centroid after runnig v.centroids?

Thanks for any help in advance!

cheers,
pipppoo
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