I have a shapefile of provinces (nxprovincias), and another shapefile of small, disconnected areas ("protected areas") that overlaps with the provinces. I want to easily calculate the total area of the protected areas within each province.
I am using QGIS 2.8.2 and all shapefiles are in the same CRS.
I have tried to "join attributes by location" - this gives an empty shapefile.
So because this didn't work, I then split the provinces shapefile up so that I have a different shapefile for each province. Then I used "clip" to clip the protected areas by province. This works perfectly for some provinces, and creates empty shapefiles for the others. Why would this happen?
Shapefiles used can be found here: https://www.dropbox.com/sh/thxvhkkoswyrldg/AAB5Lxh16uhj1WWOKVYtBj29a?dl=0
(In case anyone does try, the provinces that do not work are 4, 9, 11, 13 and 24, which all happen to be in the West of the country, for reasons unknown to me)
My question is: 1. Why does the clip only work sometimes? 2. Is there a better way to do this? I just want to know the area in each province, which seems like it should be easy to calculate?