[Qgis-user] network building tool

[Vincent Picavet]

Hello Tim,


Le mercredi 20 novembre 2013 17:40:10, Tim Michelsen a écrit :
> Dear list,
> I am looking for a tool or plugin that could help me building the basis for
> an infrastructure network (e.g. eletrical grids, gas or water piping
> network, etc.).

It all depends on the kind of lines you want between your nodes, but you could 
"easily" implement the solution you talk about with PostGIS, as it is a 
classic topo-geometry network structure.

> So the solution I am dreaming of is:
> 1) prepare a point vector layer with all nodes having unique IDs
> 	(e.g. Paris, Madrid, Berlin)
> 2) have a table where all connecting lines are listed:
>      LINE_NAME, LINE_START, LINE_END
> 	 big tube     , Paris,           , Berlin
> 	 big tube2   , Madrid,        , Berlin
> 	 big tube2   , Madrid,        , Paris
> 
> Then, a procedure would read the connections from the table and draw
> automatically these connecting lines between the nodes.

If you want straight lines between nodes, it is easy. Otherwise you would have 
to state rules for making the lines between the nodes, and it can be simple or 
very complicated to automate according to the rules.

Here is a PostGIS example of creating the edge geometry given to/from nodes :
https://gist.github.com/vpicavet/7572293

> These could then slightly adjusted manually be adding more vertices or
> alike. But the procedure would easy up the effort of building the network.
> And in the ideal case, it would also take care of updating the lines if a
> node is shifted on the map.
> (Similar to a "connector" line in an Openoffice Impress drawing)

We could add triggers to this example so that the edge line is recreated every 
time a to or from node is updated. So you would just have to edit the node 
table to have a coherent network.

This behaviour is transparent for a visualization client, QGIS for exemple.

Do not hesitate to ask for more information.
Vincent

> 
> The closes tool I found so far is the
> https://plugins.qgis.org/plugins/FlowMapper/
> But I think it's too complicated for my purpose.
> 
> I would really appreciate to receive any pointers or suggestions.
> 
> Thanks a lot in advance,
> Kind regards,
> Timmie
> 
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