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I have a road network and a geometry for each road direction. One Geometry from A->B and another Geometry from B->A. This geometries are covering each other. Is there a tool available in QGIS to select a geometry based on the start and visualise the start of the geometrie? At the end I like to have a list of all geometries in one direction which I selected.

Did I have to write a own selection tool for this usecase?

  • I doubt there's a specific tool for this, but it could be done with a geometry query. Unfortunately I don't know the specifics. First you'd have to decide how many 'directions' you want to account for - up to four would be easiest. Then you'd query against geometry coordinate values to find where start x was less than end x (left to right) or start > end (right to left), and the same for start y vs end y. There are a few questions around in the ArcGIS context that may have adaptable examples. You could also try querying for lines where start x,y match the desired start points' x,y. – Chris W Oct 28 '14 at 19:56
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If you edit the style of your line layer (Layer Properties > Style) and change the Symbol layer type from "Simple line" to "Marker line", change the symbol shape to an arrow or triangle, you can see which direction the line flows from the start:

Style properties

You can then follow this post which descibes how to reverse the line by using the Python codes mentioned or the v.flip function from GRASS.

Hope this helps.

  • Thanks for the hint. Visualisation works fine. I already have all geometries inverted in my database (both) direction. What I need is a tool select n geometries in one direction and add them to a list. – user5082 Nov 3 '14 at 17:10
  • You could set up an Action which should be able to do this, you can post it as another question if you require help. – Joseph Nov 4 '14 at 10:06

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