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

[Richard Chirgwin]

>
> ------------------------------
>
> 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