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

[M S]

nice document!  this is great stuff.

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.

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.

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!).  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.

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).


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
>
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