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

[Richard Chirgwin]

Daniel - Thanks! (Remind myself to re-read the manual for the functions 
I don't often use!)

Richard

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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>>
>>     
>
>