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My starting data :

  • a collection of points which are buildings
  • a collection of points which are electrical transformation plant
  • a network of vectors which is the public electric network from an operator
  • buildings are not connected to the electric network

I use QGIS to find which are the buildings which are located less than 250 meters from an electrical transformation plant by following the network. I need this information more 100.000 buildings.

To do it by hand :

  • trace a line between the building and the nearest electrical network segment,
  • compute the distance by the network between this entry point and the nearest tranformation plant. I have found the RoadGraph plugin (http://gis-lab.info/qa/road-graph-eng.html) which works for that
  • add the two distances and check if < 250m.

Now, my question is: how to automatize it for the 99.999 other buildings ? I know Python a lot but I am a beginner with QGIS. I did not find a way to automatically interact with the RoadGraph plugin and source code seems not to be available anymore.

Maybe I am doing it wrong ?

what it looks like

  • 1
    is your data in PostgreSQL? – kttii Jun 20 '16 at 16:05
  • No, they are in fields associated to the layers via attribute tables. If it can help, I think I would be able to export them to pgSQL. – Alexandre Norman Jun 20 '16 at 16:25
  • so your data comes from shapefiles? – kttii Jun 20 '16 at 16:42
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The PostGIS extension of PostgreSQL contains an executable (shp2pgsql) to import shapefiles (.shp) to PostgreSQL.

The pgRouting extension contains functions for the routing of networks (ways), such as pgr_dijkstra().

You could either write a stored procedure to do the automation or use python to access and automate the functions.

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