The Longest Straight Line Land And Sea Route

The red line on this world map looks all curvy, but in reality is a perfectly straight line. Remember, the earth is spherical, so any straight line drawn on the surface of the earth will appear curved in a flat projection of a map, if the line is long enough. This is why satellite paths when mapped over the earth’s surface appear like sine waves. The reverse is also true: any straight line on a flat map is actually a curved path.

This particular red line is special, because it represents the longest straight-line sea journey anybody can take without hitting land.

The image was made more than five years ago by Patrick Anderson, an environmental law attorney in Decatur, Georgia, and posted on Reddit. Patrick did not discover the path himself; he found the information on Wikipedia as a series of coordinates which he plotted them on a map. Who originally proposed the path is somewhat of a mystery. In any case, claims such as this are incredibly hard to prove mathematically because of the sheer number of paths possible.

Recently, Rohan Chabukswar, a physicist at United Technologies Research Center in Ireland teamed up with Kushal Mukherjee, an engineer at IBM Research India in New Delhi, and developed an algorithm to find a solution to the problem. Using data from the National Oceanic and Atmospheric Administration’s ETOPO1 Global Relief model of Earth’s surface, which shows the entire planet at a spatial resolution of approximately 1.8 kilometers, Chabukswar and Mukherjee proved that Anderson and his Wikipedia muse were indeed correct.

So the longest straight-line sea journey begins from the south coast of Balochistan province somewhere near Port of Karachi, Pakistan, across the Arabian Sea, southwest through the Indian Ocean, passing between Madagascar and the African continent, across the South Atlantic Ocean skirting past the Antarctic circle, then moving west after rounding the Cape Horn, then northwest across the Pacific Ocean, through the South Bering Sea and ending somewhere on the northeast coast of Kamchatka, in Russia. This route is 32,090 km (19,910 miles) long.

The researchers also calculated the farthest anybody can drive on land in a straight line without running across a large body of water. The results are a bit controversial. According to Chabukswar and Mukherjee’s find, that path stretches from Quanzhou in eastern China through Mongolia, Russia, and Europe, and ends near Sagres, Portugal. The drive is 11,241 kilometer (6,984.9 miles) long and goes through a total of 15 countries.

Longest straight-line land path according to Chabukswar and Mukherjee.

But there are other contenders to the longest straight-line land route. Again using Wikipedia as our source, the longest continuous straight-line distance in any direction on land is 13,573 km (8,434 miles), and follows along a line that begins on the West African coast near Greenville, Liberia, goes across the Suez Canal, and ends at the top of a peninsula approximately 100 km northeast of Wenzhou, China. The route goes through 18 countries.

If Wikipedia is correct, the longest land path is more than 2,300 km longer than the one claimed by Chabukswar and Mukherjee.

Longest straight-line land path according to Wikipedia

Keith Clarke, a geographer at the University of California, Santa Barbara, says that while study is interesting, the results might not be accurate. The Earth isn’t a perfect sphere but is bulging at the equator, and Clarke wonders whether the slight bulge could cause the sea path to run aground especially in the tight squeeze between Antarctica and South America. For the land model, the accuracy is limited by the resolution of the data set used, which in this case is 1.8 kilometers—anything smaller than that, such as a small lake, would be missing in the data set. So it’s possible that anybody attempting to drive over the land route might come across unexpected bodies of water. The path also doesn’t take into account any mountain range, deserts, forest and other such natural obstructions, so it certainly not drivable.

“The problem was approached as a purely mathematical exercise,” the researchers noted in their paper. “The authors do not recommend sailing or driving along the found paths.”