Calculate surface area of polygon within the lines of another polygon

Question

I have two shapefiles, both polygons.

1) The first file represents the administrative boundaries of provinces. This file contains a lot of fields. [social, geographic, natural, morphological etc] 2) The second file represents the cover of a specific type of tree. This shapefile contains some fields [the type of tree, surface area etc.]

What I want is to get the sum of the total surface area of all tree cover within a state.

I have tried multiple ways and read multiple posts, but none quite seem to do what I want to do...

I feel this is a relatively simple question. I thought I could do it with field calculator. But field calculator doesn't allow for the selection of multiple shapefiles...which I find very strange.

Answer 1

I would intersect the boundaries layer with the tree layer (Vector -> Geoprocessing Tools -> Intersect, input:boundaries, interesct: trees) in order to get a "tree layer" which is split across boundaries and has the boundary ids. After that, you can calculate statistics per administrative boundary.

Answer 2

If I understand your question correctly, you could try Vector > Research Tools > Select by Location and choose the features in the Tree cover layer which intersect with your Provinces layer. Then save the selected polygons to a new shapefile and work on that.