4

I have a large number of polygons that are overlapping. I'd like to create a heat map and plan on using raster calculation to do this. My plan: to give each polygon a raster value of 1, and adding them up. But, when I convert to raster, it will only the entire shape so that all overlapping polygons have the raster value of 1.

Can I make it convert the individual polygons? I'm doing this in QGIS but come from an ArcGIS background, so either explanation may give me enough to get this done.

  • 3
    There is a great blog post on this subject by ESRI called "More adventures in overlay: counting overlapping polygons with spaghetti and meatballs". It may give you some ideas: blogs.esri.com/esri/arcgis/2012/11/13/spaghetti_and_meatballs – Aaron Feb 18 '14 at 20:09
  • Not really great at the old indept questions but first thing that strikes me is why not do a spatial query first for the partsof a polygon which overlap? – Ger Feb 19 '14 at 9:25
  • The Parts that overlap, may actually have more than just 2 overlaps, maybe even 10 overlaps. I'm working on the spaghetti and meatballs method. Spatial join is taking a while since I had so many chopped up pieces – jpmaniac87 Feb 19 '14 at 17:03
  • Aaron, that article actually ended up being exactly what I needed. I had some issues with summing the spatial join, so had to go a slightly different way, but I got what I needed. Thanks! – jpmaniac87 Feb 19 '14 at 18:45
-1

This seems to be the ArcGIS solution. Hopefully this can guide you in QGIS.

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

  • This is excellent! Thank you. The only thing... I don't believe QGIS can do the dissolve based on the count, which is a shame. Do you know any other options or does anyone know if QGIS can, in fact, handle this? – jpmaniac87 Feb 19 '14 at 16:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.