On 28/09/17 08:51, Markus Metz wrote:
On Wed, Sep 27, 2017 at 11:55 PM, Moritz Lennert
<[email protected] <mailto:[email protected]>> wrote:
>
> On 27/09/17 21:03, Markus Metz wrote:
>>
>>
>>
>> On Wed, Sep 27, 2017 at 4:07 PM, Moritz Lennert
<[email protected] <mailto:[email protected]>
<mailto:[email protected]
<mailto:[email protected]>>> wrote:
>> >
>> >
>> >
>> > Le 27 septembre 2017 13:11:54 GMT+02:00, Johannes Radinger
<[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
a écrit :
>> > >Hi,
>> > >
>> > >I have a GRASS vector network that represents a river network (with
>> > >many
>> > >first order tributaries) and that has additional connected nodes
that
>> > >represent sampling sites.
>> > >
>> > >I'd like to extract a minimum subnetwork of the full network
that still
>> > >connects a set of selected nodes (e.g. identified by their cat).
>> > >However,
>> > >network edges (i.e. river segments) that are not necessary to
connect
>> > >the
>> > >sampling points should be excluded in the new subnetwork. Is there a
>> > >function or process in GRASS GIS to extract such a subnetwork that
>> > >fully
>> > >connects a set of selected nodes?
>> >
>> > not sure but maybe v.net.spanningtree ?
>>
>> v.net.spanningtree calculates a tree covering all nodes in the
network, not only selected nodes, therefore v.net.spanningtree does not
apply here.
>
>
> If you connect only the selected nodes to the network, wouldn't that
work ? Or does v.net.spanningtree consider all connections between lines
as nodes ?
v.net.spanningtree considers all internal nodes of the network. See also
https://en.wikipedia.org/wiki/Spanning_tree
Ok, thanks. So, one would need to "disconnect" lines at non-selected
nodes for this to work.
And maybe some clarification on what is meant by "nodes" in the sentence
"A spanning tree is a minimum cost subnetwork connecting all nodes in an
undirected network" in the man page might help future users.
Moritz
_______________________________________________
grass-user mailing list
[email protected]
https://lists.osgeo.org/mailman/listinfo/grass-user
