How do I calculate area for an island? Posted by UltraWorlds on 9 September 2017 in English. Specifically these ones if it matters.
OpenGeofiction
Discussion
Comment from Cauldron on 9 September 2017 at 12:21
If I remember correctly, if you have the measure tool open on JOSM and select the coastline of the island, it should give you the area of the entire island polygon.