How to count the number of polygons within a grid?

Question

I have two vector layers: 1) with polygons representing landcover types and 2) a grid, overlapped with the first one.

I want to obtain, for each square within the grid, the number of land cover types. For example:

In the red square it would have 2 landcover types (2 and 7), and the left square to that one only 1 land cover type (2).

How do I obtain this values, using QGIS?

Answer 1

Add a virtual layer (layer > add layer > add/edit virtual layer)

Import both grid- and landcoverlayer

In the query-window you can add following code. In the code you will have to change grid, landcover and type to what your layers and attributes are named of.

select grid.*, group_concat(landcover.type) as types from grid, landcover where st_intersects(grid.geometry, landcover.geometry)

Now you should get a new layer with a grid extended by an attribute called 'types'

Answer 2

If you want to count the number of polygons within your grid, you may use the Join attributes by location tool from the Processing Toolbox.

For your specific case, these parameters should work:

The output of the tool will be a grid layer which stores the number of the intersected polygons in a new field, called "count".