[GRASS-user] v.centroids question

[Nikos Alexandris]

On Wed, 2008-03-19 at 10:20 -0700, John C. Tull wrote:
> I have a road network where I want to convert the road lines into  
> boundaries, then turn the resulting spaces inside of roads into areas.  
> Converting the roads to boundaries was no problem using v.type and  
> v.clean tool=snap, but getting centroids into the polygons is  
> trickier. Apparently, v.centroids will not add centroids to areas  
> where there are boundaries that terminate inside a polygon (i.e., dead- 
> end roads inside what I am hoping to turn into an area), so I end up  
> with far fewer areas than I want. Do boundaries have to be contiguous  
> without dangles (is that the right use of the terminology?)?
> 
> Is there a way to get centroids into areas such as these where the  
> road dangles are ignored? I don't want to drop those dead-end roads  
> because they are informative, but I guess I may have to do so and then  
> use v.overlay or similar at a later stage. There are also too many  
> potential areas to try and manually add the centroids with v.digit.  
> Perhaps there is a means in v.edit unknown to me. Any ideas or  
> suggestions would be greatly appreciated. I am using GRASS 6.3rc5.

John,

maybe you could try 

v.clean with type=line,boundary,centroid,area tool=snap,break,rmdupl
thresh=.01

Not sure but I suspect the "break" tool is what you might need.