Counting buffer overlap in QGIS

Question

For my thesis I'm modeling the identification of recreation areas. Therefore, there has been a survey where people were asked to specify where they recreate. They had to indicate this place on a map and give a radius. Now I have to analyse which areas were most visited, and afterwards use the data to give a weighted rating with the travel distance.

So, I use QGIS to Buffer the data points by using the given radius. Now, I want to calculate for every point in the country how many times it was visited.

Any thoughts how to do this in QGIS?

Answer 1

You could use the Intersect tool (Vector > Geoprocessing Tools > Intersect) on the buffers and then to find the number of intersections it would simply be the total number of attributes - the number of points.

Answer 2

Here's a blog post by Paul Ramsey about doing this in PostGIS, perhaps a worthy venture:

http://boundlessgeo.com/2014/10/postgis-training-creating-overlays/

Summed up with this note:

Now we have a single coverage of the area, where each polygon knows how much overlap contributed to it. Ironically, when visualized using the coverage count as a variable in the color ramp, it looks a lot like the original image, which was created with a simple transparency effect. However, the point here is that we’ve created new data, in the count attribute of the new polygon layer.