1.8 meters sees ~4.8km. Standing on top of a car, on someone else's shoulders, at say, 5 meters, would give you eight kilometers.

Granted, not too drastic yeah. But like, if you have a tree, and climb it, and it's, say, 15 meters. Now you can see ~14 kilometers.

I'd say going from ~5 to ~14 by climbing a tree (or a mast of a ship) is pretty significant, but not drastic, I'd agree to that, yeah.

I wonder how much it was an advantage at sea, really. Like the scout at the top of your mast would be able to see the enemy ship from very far, while the enemies would technically be able to see only the mast of the ship that the scout is on, making it much harder to spot. I'm sure someone's written about it in tedious length. An upvote to anyone who finds me such texts.