[GRASS-user] RE: Network Analysis output in GRASS

Hamish hamish_b at yahoo.com
Tue Jun 9 22:55:38 EDT 2009

Donald wrote:
> I am returning to GRASS after a 10 year hiatus and I must
> say that I am impressed ! 
> I am working on some simple network analysis (road
> distances from a point) and want the output to appear as
> concentric rings.  I think I need to use v.net.iso on
> my road network but  it appears from the manual that
> the output from v.net.iso is a line file.  I'd like to
> push that out to a polygon to get concentric rings so it
> looks like I need a few more processing steps. 
> Like I said, it has been a long while since my GRASS4.0/4.1
> days - what would people suggest using to push the output of
> v.net.iso out to a polygon ?  v.surf.idw, v.surf.icw,
> v.hull ?  Aren't these all point interpolations and I
> need to interpolate from lines ?

perhaps "v.to.db option=start/end" to get endpoints and then
string them together into a new vector line or run v.hull?

or similarly but with 'v.to.points -n'.
getting the line vertex order right might be a pain.

v.hull isn't the best as it cuts across "bays" in the blob, but
other than manual approaches (like above or digitizing by hand
around the lines with v.digit then snapping to underlying vertices), I'm not sure. Keen to hear any other solutions though.



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