> Consider the default zero-zero GPS coordinates (and use an app for plane or shipping tracking to look at it). It's about 200 miles off the coast of Africa and there are thousands of dodgy transponders identifying various vessels as being located there.

There actually is a weather bouy at 0, 0. It's mapped in OpenStreetMap with a note of "This is actually here, it's no a bug"

    https://www.openstreetmap.org/node/3815077900