[GRASS-user] Extract subnet from grass vector network based on selected nodes

[Markus Metz]

On Wed, Sep 27, 2017 at 11:55 PM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:
>
> On 27/09/17 21:03, Markus Metz wrote:
>>
>>
>>
>> On Wed, Sep 27, 2017 at 4:07 PM, Moritz Lennert <
mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>> wrote:
>>  >
>>  >
>>  >
>>  > Le 27 septembre 2017 13:11:54 GMT+02:00, Johannes Radinger <
johannesradinger at gmail.com <mailto:johannesradinger at gmail.com>> 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

Markus M
>
> Moritz
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