You seem so snarky but to be honest you are kind of embarrassing yourself in my opinion. Sorry. He's not just looking at them. Their height is measured by sea level, not some fool with a tape measure from the ground... So knowing the height, as measured from sea level (barometricly I believe), allows their position relative to one another to shed quite a lot of light on what the shape of said level would be or at least how it expresses itself across a predetermined distance.