Do human-made structures account for the Earth's curvature?
If the Earth is round, some of the largest human-made structures would have to take the Earth's curvature into account during design and construction. For smaller structures like individual buildings this wouldn't matter but for things such as very long bridges it would become an issue.
In fact it is an issue and it does happen. A well-known example is the Verrazzano-Narrows Bridge in New York. With a central span of 1,298 m (4,260 ft), it was the longest suspension bridge in the world when it was built in 1964. Its two suspension towers are 211 m (693 ft) tall and 1,298 m (4,260 ft) apart. Although each tower is vertical and perpendicular to the water, they are 41.28 mm (1 5⁄8 in) farther apart at the top than the bottom. This is due to the Earth's curvature.
Another example is London's underground train system. When the Crossrail tunnels were built in the 1990s, the Earth's curvature had to be included in the calculations to avoid misaligning them1.
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Author: Dave Owen