[GRASS-user] breaking out ("rescuing"?) islands

[Hamish]

David Norris wrote:
> The short story: Is there a way to "rescue" islands from vector areas? 
> In other words, "break" the area up? This is hard for me to put into 
> words, so I've drawn a picture to help explain what I want to do:
> 
>     <https://netfiles.uiuc.edu/danorris/www/rescue-islands.png>
> 
> The long story: I know it isn't topologically correct to do this. The 
> problem is that I'm exporting this data as a shapefile for use in 
> another program -- and that program doesn't understand "rings" in 
> shapefiles! It sees all rings as outer rings, and doesn't understand 
> holes. The only way to make this program see the existence of the hole 
> would be to break up the polygon as in the diagram above so that it can 
> be represented with one simple outer ring. I don't need the data to be 
> modeled this way inside GRASS, just in the exported shapefile (or any 
> other format that I could then translate into a shapefile).
> 
> Aside: I know the proper solution would of course be to add outer/inner 
> ring support to this external program, but unfortunately that's not an 
> option. It's a kludge, but it's the only way I can think of to get valid 
> data into this program!


maybe forget about areas and export as lines?

v.type "boundary,line"



Hamish