Measuring The Curve

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Here... the curve is here. In fact, smart people have already calculated the curvature. You can use this calculator to conduct your own experiments.

There are, however, some caveats to conducting your own line of sight experiments. First, you will need a long surface that closely the surface of the earth. Such a surface is usually a liquid body because it conformed to the earth's shape, whereas a solid structure could take any shape (I.E. mountain, plateau, crater, etc). Second caveat is that a clear day is usually necessary. Without a clear day, the object might not be viewable from a distance that would normally be viewable. Third, you're going to need powerful camera or a telescope. A number of people have tried to used generic binoculars but even the world's most powerful binoculars can only view up to 45 miles. They also cost about $2,000. The average beginner telescope for under $100 can get you the distance you're looking for.

Understanding the horizon curve

Earth Curvature Calculator

The image at the top of the article is from Lake Pontchartrain, in Louisiana. There is also a causeway across the 24 mile lake, in addition to the power lines. The design of the lake and the objects over the lake makes it the perfect case study in how engineering only works on a globe.

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In order to see the curve on these long items, one has to be at ground level with a long zoom camera like a P900. This is because the curve becomes more visible as the viewer is able to get near the object and look down it. Much like inspecting a pool cue for bends. They are hard to notice unless you look down the cue, not at the side of the cue. The closer the eye ball is to the cue, the more rolls and lumps they can see in it. The same concept applies to inspecting lumber at the hardware store. Always look down the length of the board to find if it's warped. Thus, just standing above or at a distance from the causeway won't easily provide a view of it's curvature.

Additionally, engineers have to account for the curve of the earth. As an engineer myself I can assure you that we measure and design around Earth's curve and not just for long bridges or tunnels. Even calculating GPS coordinates through triangulation requires a formula that accounts for the Earth's curve. Old time sailors also had to account for the curves.

Image of Lake Pontchartrain power lines from Soundly and image of causeway is from an unknown original source.