Can he do interferometry and just have a 3rd but normal eye?

I mean, it’s a sunny day FFS!

Is the unit ‘one league’ used in LOTR (esp in elvish) the same as in our universe. Just asking as nobody here is questioning the units.

I could be entirely wrong about this but isn’t it in-universe lore that Elves don’t see the curvature of the world and that’s how they can see so far?