vector extraction

[Paul Loechl]

In an E-mail message, Bill Jackson wrote:
> 
> Is there a GRASS4.1 program available for "clipping" a subset of a vector
> file outside of v.digit? 
> 
> Occasionally when editing a vector file lines can be unintentionally deleted.
> The cursor can be placed on the line to be deleted and another line. Often
> a larger line segment, nowhere close to the original line, will be highlighted 
> instead and can get zapped. Of course, if you are careful this shouldn't happen
> but when it does it is a real hassle, especially on large files. 
> 
> Normally, I would make a copy of the original vector file and then edit it with
> the block line delete tool to try to isolate the line or lines that were 
> accidentally deleted and then use v.patch to repair the file. 
> 
> It would be great to be able to take a subset of a vector file as easily as
> using r.mapcalc map1=map2.
> 
> 
> If there is not a tool available to do this I will try to write a shell.
> 
> 
> Thanks
> 	Bill Jackson
>  
> 

Try using v.cutter to extract a subset of a vector file.  v.cutter allows you to 
specify a cookie cutter template such as a boundary line.  This cutter template
selects only lines and polygons inside of it.  The output is essentially a masked
version of the original vector map.  BE SURE to run the v.spag program on the 
resultant file to remove any identical lines.

-- 
-------------------------

Paul Loechl					loechl at zorro.cecer.army.mil
USA CERL					(217)352-6511x668