[GRASS-user] Extracting the external boundary of a vector file

[Nikos Alexandris]

On Thu, 2008-05-29 at 09:41 +1000, Edward Tomlinson wrote:
> Hi list,
>  
[...] 
> My problem is however, i want to create another vector file that
> contains the mask or the external (an internal island) boundary.
>  
> I have been able to create the external boundary fine through the
> following.
> v.category (delete categories)
> v.category (add category as 1 for all)
> v.dissolve (combine all boundaries with common category)
>  
> This is great and works fine for the external boundary. However there
> is meant to be an island in there. Somewhere along the way (i think
> after the second call to v.category) it fills that island in.
>  
> Has anyone got any hints or ideas?

If it is about one "area" only what about removing it's centroid before
dissolving (I guess) ?

[...]

Nikos
>