For OpenStreetMap names transliteration to Latin characters, I need to know whether a point (latitude, longitude) should be transliterated to Japanese or Chinese.
f(latitude, longitude) would tell whether the point is in Japan or China?
It does not need to be perfect, especially since there are islands whose status is disputed.
For transliteration purposes Taiwan is better included in the Chinese-speaking zone.
The goal is actually for the Android app OsmAnd to decide on-the-fly for thousands of labels which language to show, so it must be extremely fast, and must be able to work offline.