[GRASS-user] making an area with existing lines

Micha Silver micha at arava.co.il
Sun Mar 22 02:29:54 EDT 2009

hardinej wrote:

> Hello,
> I have two vector lines and I want to limit operations to the the area in
> between these lines. I've had some ideas about how to do this, but I really
> don't know how to. I don't know if this extra info would be useful, but here
> it is: the lines are a road and a shoreline, the are roughly parallel, and
> they do not cross. At first I thought maybe I could export them as ascii,
> concatenate the list and import as an area, then convert to a raster that I
> could use as a mask. I don't actually know if this would work because I was
> having some troubles exporting the vector files, they were blank. But
> anyway, if anyone could let me know what they think, that would be great. 
> Thanks,
> Eric 
Depends on what operations you're planning. vector? or raster?
For raster, I'd make the two parallel lines into a closed boundary 
(using v.digit) and also digitize a centroid. THen I'd change the vector 
area to a raster (v.to.rast type=area ...) and finally use that raster 
as a mask. Now all raster operations will be limited to the area between 
the two lines.
If it's vector operations, I'd guess that you'll again want to create a 
closed boundary with a centroid, and then, after running whatever 
operations you have in mind, just do "v.overlay operator=and ..." to get 
results again only in between the parallel lines.

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