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I am trying to illustrate travel using a flow map on a road layer. My data is:

  • city of origin
  • destination
  • number of travelers

How do I use a polygon city layer (or point) and a road layer, with line thickness representing volume of travelers?

I am using QGIS.

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  • Do you have a layer that has the following fields: From, To, and travellers? If not, you might have to build a line layer from your point layer (City nodes) and your text data (Number of travellers). Please clarify!
    – dassouki
    Apr 26, 2013 at 19:01
  • i would have to build that layer, it is in my SQL database. I dont have it qgis yet. I am curious about the process of overlaying the travel on to the road network, what pluggin to use? thanks!
    – user17543
    Apr 26, 2013 at 19:07
  • Do you also have to do the routing algorithm from city to city? or is it going to be a straight line? or do you know the roads that they will take? How many points do you have to do this for? I'm just curious if you can edit the question and be very detailed about the specifics and requirements, and based on that I can perhaps post an answer. As of yet, it seems some details are missing, and it'll be very crucial to understand what data you have, what you're trying to accomplish, so a detailed / direct answer could be provided
    – dassouki
    Apr 26, 2013 at 19:12
  • The data I have: city From, To, and Travellers. no actual data on their route, but it is safe to assume they take the shortest route. There are two main highways through the Canadian rockies and the map is hoping to show where snowmobilers come from and go to, to help the avalanche centre better focus their efforts on road side safety info. I would like the travel to follow major roadways, as it will look a lot nicer than a bunch of point to point lines.
    – user17543
    Apr 26, 2013 at 19:21
  • Don't snow mobiles have their own trails but they can cross highways at certain locations? I'm just scared that this could be a problem a lot bigger than you anticipated initially. However, I'm not sure if you know this but you can edit your original question to reflect the additional information you provided.
    – dassouki
    Apr 26, 2013 at 19:23

1 Answer 1

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If you would like to automatically depict from node to node straight line segments (say flows); you can check for the Flow Mapper QGIS plugin.

Provide input nodes and interaction matrix between nodes as white space deliminated text file, then plugin will automatically generate them in a shapefile.

http://plugins.qgis.org/plugins/FlowMapper/

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