The Longest Straight-Line Paths on Earth: Sailing or Driving Without Turning
Longest Straight Line Paths on Water or Land on the Earth (2018)
This paper tackles a deceptively simple question: what's the longest straight line you can travel on water without hitting land, and conversely, on land without hitting a major body of water? The problem is chaotic due to islands, lakes, and fractal coastlines. The authors present a branch-and-bound algorithm to compute both paths, offering a rigorous method for these extreme geographic optimizations.
In its basic form, this is an optimisation problem, rendered chaotic by the presence of islands and lakes, and indeed the fractal nature of the coasts.
- ventana
The paper is basically like this (spoiler alert):
“Some random user on Reddit posted a picture claiming that this is the longest straight line path on water possible on the Earth. We implemented a smart algorithm to solve this problem, found the elevation data, ran our algorithm... yes, that random user was right. Also, here's the longest path on land.”
Thanks, I really enjoyed reading it, even though I hoped that they would disprove the original claim!
Edit: here are the gcmap links to the two paths: sea [1], land [2].
[1]: http://www.gcmap.com/mapui?P=25%B017%27N+66%B040%27E-58%B037...
[2]: http://www.gcmap.com/mapui?P=24%B033%27N+118%B038%27E-37%B02...
- gcanyon
I know the globe is unintuitive (it still blows my mind that Muslims in New York City face roughly northeast to point toward Mecca) but it still seems bizarre that the water route can start near the arctic circle, cross the Pacific ocean, nearly touch Antarctica, cross the Atlantic ocean, and cross the Indian ocean to end well north of the equator and still travel only 80% of the way around the globe. This view of the rest of that great circle helped me visualize it: http://www.gcmap.com/mapui?P=58%B037%27N+162%B014%27E-25%B01...
- OscarCunningham
There's a longer land path that starts in or near Senegal and ends in China. But they miss it because it goes near the Dead Sea, and they treat anything below sea level as water.
- mdritch
It reminds me of a bit I did a few years ago trying to find the
"longest straightest" line in Atlanta [PDF]: https://matthewritch.com/pages/LongestStraightestLine.pdf
- mrgriscom
I made a "first person" perspective rendering of this: https://mrgris.com/img/landfall/longest.png