from Eurogamer interview:
on ranged units:
Jon Shafer: We've also got a brand new terrain system that's been built from the ground up for Civ V. It's not easy to make a system that can build a truly random map that always looks good, it's something that hexes have helped us with.
Eurogamer: Sorry to ask a purely functional question, but there's something I'm not clear on - how do you decide what archers can see and what they can shoot?
Jon Shafer: They can shoot over things, if they're up a hill. The range is the same, but if they're in a jungle, all they can see is the jungle. But if they're on a hill and there's a forest between them and the enemy, they'll be able to shoot over it
on ranged units:
Jon Shafer: We've also got a brand new terrain system that's been built from the ground up for Civ V. It's not easy to make a system that can build a truly random map that always looks good, it's something that hexes have helped us with.
Eurogamer: Sorry to ask a purely functional question, but there's something I'm not clear on - how do you decide what archers can see and what they can shoot?
Jon Shafer: They can shoot over things, if they're up a hill. The range is the same, but if they're in a jungle, all they can see is the jungle. But if they're on a hill and there's a forest between them and the enemy, they'll be able to shoot over it