I have a shapefile with many polygons. Some partly overlap with each other, some are not overlapping. I'm considering a polygon to be overlapping given a minimum area of overlap. 'Islands' of partly overlapping polygons occur. I'm interested to find out how many islands are there and which polygons are forming them.
I can use ArcGIS 10.2 and/or OGR, both with Python but I'm not sure how to proceed. I know there is an overlap function in OGR but it just finds overlapping polygons. Is there maybe functionality already available which does the above?