I'm using QGIS 2.12.0 and am trying to formulate a hierarchy for the risk factor associated with footpath polygons based on their proximity to pedestrian generators and the importance factor of that generator. For example, a bus stop will have a buffer radius of 100m and a factor of 10, while a small park will have a radius of 400m and a factor of 5. When the buffers are created, it's obviously going to create several hundred overlapping buffers and I wanted each intersecting segment to inherit a cumulative factor based on the overlapping factors (I've tried to illustrate what I mean in the pic). Heat maps using the factor work ok, but they don't take the radius into account.enter image description here

Does anyone have any ideas how I might go about achieving this?

  • I'm not sure how you would go about getting the cumulative buffer values but you could try doing a raster weighted overlay analysis. You could try to make different rasters for your factors (converting the buffer polygons to raster) and overlay them ( this is what I've seen people do normally ) – Hasan Mustafa Mar 21 '16 at 4:53
  • To get the sum of the buffers you can try Join attributes by location in Data Management in the Vector Menu ( it will result in a new shapefile but it does give the option of sum ) I'm not sure if this will work or not. – Hasan Mustafa Mar 21 '16 at 6:15
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    Is it possible for buffers having same radius and factor to overlap? And should in this case factors sum up? As result do you need polygons or a raster? – Detlev Mar 21 '16 at 8:58
  • Hasan, the Join attributes by Location was not successful - in fact, it crashed everytime I tried to run it - perhaps because of the number of buffers involved. Detlev, I do want the buffers with the same radius and factor to overlap and sum - as for the final result, I'm not fussed if it's a polygon or a raster. I appreciate the help! – Anthony K Mar 22 '16 at 22:01

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