I want to identify all beaches on this planet (or a given subset of it) that are facing westwards (+/- 20-30 degrees).
My idea is to use OSM as the data source. Extracting all polygons that have the tag "natural=beach" gives me a dataset / shapefile of all areas that are flagged as beaches. So far so good.
I also know that I can use coastline data (either from OSM or Natural Earth for example) to identify the facing of the beaches.
Buffering the beach shapes to correct for minor mismatches and intersecting these with the coastline should provide me with data on which side of the shape is facing towards the water. Using the max/min values of all intersecting points should give me an idea of the bearing. (90 degrees +/- 20-30 degrees would be fine...)
And that's where I am lost...
My preferred tool would be QGIS, but PostGIS would be OK as well.
Is there anyone around with a clever idea how to solve this puzzle?