[GRASS-user] v.net.iso - service area

[David Mahoney]

I went through this last year, and as I remember, v.hull doesn't quite
get you there, since the resultant polygon can't "dip in" to reach
concave sections of a service area. I used v.delaunay to create a
network of the nodes that made up the connections between service areas,
and v.net.salesman to generate the edges of the service areas.

David

On Mon, 2010-04-05 at 09:04 -0300, Daniel Victoria wrote:
> If I understand you correctly, v.hull might help to create the service
> area polygon from the points....
> 
> http://grass.itc.it/grass62/manuals/html62_user/v.hull.html
> 
> On Sun, Apr 4, 2010 at 8:12 PM, Richard Chirgwin
> <rchirgwin at ozemail.com.au> wrote:
> >>
> >> ------------------------------
> >>
> >> Message: 3
> >> Date: Sat, 03 Apr 2010 23:11:26 +0200
> >> From: "Johannes Sommer" <Johann.online at gmx.de>
> >> Subject: [GRASS-user] v.net.iso - service area
> >> To: grass-user at lists.osgeo.org
> >> Message-ID: <20100403211126.313360 at gmx.net>
> >> Content-Type: text/plain; charset="iso-8859-1"
> >>
> >> Hi list,
> >>
> >> recently I played around with the network functionality in ArcGIS. I
> >> generated so called "Service Areas" in a network dataset which return the
> >> regions that can be accessed in a network dataset based on several distances
> >> (in my example 150, 400 meters).
> >>
> >> I wanted to reproduce the results with GRASS GIS and after a short search
> >> I found the module v.net.iso which seemed to fit my needs. It returns
> >> exactly the same results as ArcGIS did on isolines on a network, but I can't
> >> find any solution concerning the service areas.
> >>
> >> Can anyone point me in the right direction to calculate zones (that is
> >> "build polygons from the end points of each network segment") from these
> >> generated isolines in a network?
> >>
> >> Regards,
> >>
> >> Johannes
> >>
> >>
> >>
> >
> > Johannes,
> >
> > I don't think there's anything to do this automatically in Grass-GIS. But I
> > think you should be able to construct a script that would connect pairs of
> > points.
> >
> > So if you can extract each end point of the network segment, you would end
> > up with a vector containing only points - then create a temporary map of a
> > point pair, run (say) v.distance output=connectors on each point pair, patch
> > the resulting maps together ...
> >
> > It sounds a bit labourious, and probably someone else can think of something
> > easier, but if you get all the individual steps right, a script is then easy
> > to create.
> >
> > (Actually, Johannes, I think the idea is brilliant. I've done lots of
> > network service area work, and it never occurred to me before!)
> >
> > Richard Chirgwin
> >
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