[GRASS-user] Re: [GRASSLIST:1098] v.net.steiner

[M S]

seems like the terminals are identified by a layer number and range of
categories.

how do you get the layers associated with each feature type like arc, node,
point? to input into the function?

are the categories created while numbering basic elements first, and then
complex ones?  meaning if you have two nodes and an arc, would the category
number for the arc be 3?


On 6/14/06, Markus Neteler <neteler at itc.it> wrote:
>
> On Wed, Jun 14, 2006 at 08:52:37AM -0400, M S wrote:
> > nice document!  this is great stuff.
>
> Thanks. And note that data elaboration with the current
> 6.1-CVS is even easier...
>
> > The v.net.steiner seems to be a realistic functional model by using an
> > existing (road) network to know what physical routes it can follow to
> the
> > given terminals.  this looks fantastic, and i cant wait to build some
> test
> > data.
>
> There should be a roads_net in spearfish6.0 which was recently
> updated by Radim.
>
> > is there a function (raster or vector) that would allow for building the
> > network links/lines by inputting only the points without regards to an
> > existing (road) network?  (using something like the minimum spanning
> tree
> > example below).  This function would be great as a first cut in network
> > analysis.
>
> You could use v.hull and then v.type to make it lines or use
> v.extract to only extract the boundaries, then v.type for
> boundaries -> lines. (untested)
>
> > the page below illustrates the minimum spanning tree, but if i
> understand
> > right, just nodes are inputted.  then the algorithm does at a minimum 3
> > things 1) identifies clusters of sites 2) builds the links to connect
> the
> > clusters to each other, and 3) then finds from each cluster, the nearest
> > point to other clusters.
> > http://www.cs.sunysb.edu/~algorith/files/minimum-spanning-tree.shtml<
> http://www.cs.sunysb.edu/%7Ealgorith/files/minimum-spanning-tree.shtml>
> >
> > i dont think the v.net.steiner function does what the steiner-tree
> function
> > below illustrates, because the GRASS version uses an existing (road)
> network
> > to realistically model the existing pathways (nice implementation!).
>
> Kudos to Roberto Micarelli and Radim.
>
> >  This was the steiner tree example from the same site.
> > http://www.cs.sunysb.edu/~algorith/files/steiner-tree.shtml
> > I'm working with a Network Engineer on using GRASS to solve the network
> > analysis problems.  Using the NON-GRASS steiner tree (from example
> above)
> > wont work becuase as it goes to build the links, but connects lines to
> > lines, rather than given nodes.  in the network implementaion this would
> be
> > a mid-span junction, or splicing the fiber at this junction to connect
> the
> > lines.  the minimum spanning tree is more applicable.  However, i
> suspect
> > that the GRASS minimum steiner tree is the most applicable and realistic
> > model/function.
>
> It would be great to have some examples online, for
> http://grass.itc.it/applications/index.php
>
> > The GRASS minimum steiner tree is a realistic functional model that uses
> > real network data in conjunction with the terminals.  this seems like a
> > great deployment of the steiner tree in conjunction with consideration
> to
> > the existing network such as roads.  I cant wait to have some fun with
> GRASS
> > and give this a whirl!
> >
> > as usual, keep up the great work, and thanks to everyone who makes GRASS
> GIS
> > be all it can be!  feels great to find a GIS like this one which is fun
> to
> > work with, and has such community invovlement.  truely a great
> environmant
> > that makes GIS fun (again for me).
>
> Welcome!
>
> Markus
>
> >
> > On 6/14/06, Markus Neteler <neteler at itc.it> wrote:
> > >
> > >M S wrote on 06/14/2006 03:13 AM:
> > >
> > >> The input parameter seems to be terminals.  Can they be points?
> > >
> > >They can be points (nodes) which have to be connected to the network.
> > >You may take a look at:
> > >http://mpa.itc.it/corso_dit2004/grass04_4_vector_network_neteler.pdf
> > >slide 19
> > >
> > >Markus
> > >
> > >_______________________________________________
> > >grassuser mailing list
> > >grassuser at grass.itc.it
> > >http://grass.itc.it/mailman/listinfo/grassuser
> > >
>
> --
> Markus Neteler     <neteler itc it>       http://mpa.itc.it
> ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica
> MPBA - Predictive Models for Biol. & Environ. Data Analysis
> Via Sommarive, 18        -       38050 Povo (Trento), Italy
>
> _______________________________________________
> grassuser mailing list
> grassuser at grass.itc.it
> http://grass.itc.it/mailman/listinfo/grassuser
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20060615/f13be253/attachment.html