In QGIS, I need to calculate the share of a given field (outlined) that is covered by the blue areas, see the image for illustration. Fields and blue areas are in two separate layers. I did the area calculations for each layer in QGIS, so I have the area in square meters for both the fields and the blue areas.
I already tried spatial join with the mmqgis plugin, but i can't get it to work correctly. For example, the largest blue area, clearly lying within the field in the middle, is not assigned to that particular field in the . Maybe I am just using the plugin wrong.
EDIT: It should be mentioned that i used the multipart to singlepart tool on the blue area-dataset, as some of the individual blue areas was "connected" though they looked separate on the map.
Using the intersection tool as proposed, i got a dataset with more rows than the dataset containing the "blue" areas. The image below illustrates a field with two areas, but the dataset has many extra rows, which doesn't seem to correspond to a visible blue field on the map. If i select the rest of the rows, no visible parts of the map lights up.
When i run the intersect tool, it warns me that the two layers doesn't use the same coordinate system. Could this be the problem?