[GRASS-user] Vector Topology: how to get a line from a boundary

[Martin Landa]

Hi,

>> 1) How to get "just the outline" of the island ? Both v.type and v.extract
>> with "type=boundary,line" produce an empty vector.
>
> The manual reads:
>
> ---
> NOTES
>
> Only features with a category number will be extracted. So if you want
> to extract boundaries (which are usually without category, as that
> information is normally held in the area's centroid) you must first use
> v.category to add them.
> ---

you should be to extract boundaries without category by setting
'layer=-1' , e.g.

v.extract in=landcover out=b type=boundary layer=-1 new=-1

Martin

-- 
Martin Landa <landa.martin gmail.com> * http://gama.fsv.cvut.cz/~landa *