I need to show parts of a network, which meet two criteria at the same time. So I would like to use the style of criteria 1 and the style of criteria 2 side by side (see picture). The problem is, that the orientation switches for every part of the network (like in the red circle). Why? I used a +0,4 offset for the green line and -0,4 for the magenta one. Where is my mistake or is it not possible?

enter image description here

  • 1
    What software are you using? – ArMoraer Apr 19 '16 at 18:23

The problem is, that the orientation switches for every part of the network (like in the red circle). Why?

The orientation of your offset changes from one side to the other for some parts because these parts were drawn into your GIS in the opposite direction.

Lines are drawn from a From/Start point to a To/End point, and if you offset a line the offset is based on your drawn direction. A positive offset value will move the line to the right, a negative offset will move it to the left.

So if a line is drawn from South to North with a positive offset, the new line will appear to the East (to the right of the drawn line), but if your line is drawn from North to South the new line will appear to the West (still to the right of the drawn line).

Best way to picture this is to imagine you are walking along the line in the direction it's drawn - on your right will be positive offset, on your left will be negative offset.

enter image description here

To get the lines to display the way you want, I can see two possible solutions.

  1. It could probably be scripted to flip your lines to match the orientation of the other lines by detecting start and end points for intersecting lines.
  2. Merge your lines so that all the different segments become one line. This is the quickest and easiest, but will leave you with a new dataset and potentially less attributes than in your original. For a one-off this is the way I'd do it - keep my original but display the new merged line.
  • I'll try to add some images to clarify when I get in the office – Midavalo Apr 19 '16 at 18:47
  • Thanks. Is there a way to have the styling the way I want it to be in spite of this problem? – Phil Apr 19 '16 at 18:48
  • @Phil I've added a screenshot for clarity and a couple of possible solutions. – Midavalo Apr 19 '16 at 19:42
  • Tried solution 2 and made a selection with the network parts I needed and merged them into on single line feature. Still the same picture. Solution number 1 is above my abilites. I have yet to start learning python. – Phil Apr 19 '16 at 21:06

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