Because of your detachment from the ground, there is no perception of height when you are standing in a balloon. Your eyes, being positioned in front must triangulate a linear relationship with what you see in order to determine distance. Unlike standing on a building or other structure, your disconnection from the ground in a balloon disables your depth perception, so people do not sense height or experience vertigo. Even people who believe they will have a problem usually discover they feel quite secure moments after we launch.