The Longest Straight Line at Sea
Point a boat southwest off a beach in Balochistan, hold one heading, and you will not touch land again until Kamchatka — 32,090 kilometres later, four-fifths of the way around the planet.
The longest straight-line path across water on Earth: 288°35′ of a single great circle, from Sonmiani, Pakistan to the Karaginsky District, Kamchatka. Claimed on Reddit in 2012, proved optimal in 2018.
§ 01 · Two addresses
A beach in Balochistan, a shore in Kamchatka
Both ends of this line are ordinary places. That is the point — the ocean picked them, not a harbourmaster.
The start · 0 km
Sonmiani, Pakistan
25°17′N 66°40′E
A fishing coast in Las Bela, Balochistan, roughly 90 km northwest of Karachi. Nothing about the town chose this line — the shape of the world's coastlines did.
Landfall · 32,090 km
Karaginsky District, Kamchatka
58°37′N 162°14′E
A near-empty stretch of the Kamchatka Peninsula's east coast, in the Russian Far East. It is simply the first solid thing in the way.
- Angular length288°35′ of a 360° great circle — 80.1% of a full lap of the planet
- Initial headingAbout 213° — south-southwest out of the Arabian Sea (derived from the published endpoints)
- The short wayThe same two points are only 7,939 km apart across the other arc — but that arc runs over Asia (derived: 71°25′)
- In sea terms17,328 nautical miles. At a steady 5 knots that is about 144 days at sea (illustrative arithmetic, not a passage plan)
§ 02 · The milestones
Seven moments on a voyage with no turns
Everything that happens on the line, laid out by distance from the start.
Distance from Sonmiani along the great circle · milestone positions derived from the published endpoints
§ 03 · The dive south
To miss every continent, go almost to the ice
A straight line on a sphere is not a straight line on a map. Here is what the boat's latitude actually does.
Latitude of the line against distance sailed · crosses the equator at 3,273 km and again at 23,288 km
Southernmost
60°22′S
13,280 km in · 38°55′W
Deep in the Southern Ocean, closer to the Antarctic coast than to any port.
Equator crossings
2
3,273 km · 23,288 km
Once heading south in the Indian Ocean, once heading north in the Pacific.
Final stretch
8,802 km
Pacific equator → landfall
The longest run on the whole line without a gate to thread.
§ 04 · Three gates
Where the line threads a needle
On a 32,090 km path, the whole result hangs on two narrow gaps and one long empty run.
Gate 1 · 5,835 km
Mozambique Channel
419 km at its narrowest
Between mainland Africa and Madagascar, over water 3,292 m deep. Close the gap and the whole line dies here.
Gate 2 · 14,941 km
Drake Passage
≈115 km south of Cape Horn
The 800 km gap between Cape Horn and the South Shetlands — and the throat of the Antarctic Circumpolar Current, 173.3 Sv of moving water.
Gate 3 · 28,918 km
The Aleutian approach
North Pacific, 42°N 160°W
The line runs up the open Pacific and slips south of the Alaskan island chain before Kamchatka stops it.
§ 05 · How it was proved
Five trillion points, ten minutes
A Reddit map in 2012, a proof in 2018 — and the same answer.
Straight-line distances, kilometres · one hue, light to dark
Great circles to check
233,280,000
at 1 arc-minute resolution
Points to classify
5.04 trillion
21,600 per great circle
Time to the answer
≈10 minutes
branch & bound, standard laptop
The claim started as a map posted to Reddit's r/MapPorn on 29 December 2012 by a user called kepleronlyknows. Six years later, Rohan Chabukswar and Kushal Mukherjee rebuilt it as an optimisation problem: enumerate every great circle, read NOAA's elevation grid along it, call anything above sea level land, and keep the longest wet segment. Branch-and-bound let them discard whole families of circles at once instead of walking all five trillion points. The answer was the same line the Reddit map had drawn by hand. The land equivalent — 11,241 km from Jinjiang, China to Sagres, Portugal, across 15 countries — took 45 minutes.
§ 06 · The fine print
What this map is not
Every optimum comes with the assumptions that produced it.
- Sea level decidesLand is anything with a positive elevation in ETOPO1, water anything negative. Rivers, low plains, bridges and sea ice are invisible to it.
- 1.855 km per pixelThe grid is 1 arc-minute. Real coastlines are fractal; a finer dataset could shift the answer.
- A perfect sphereThe maths assumes one. The Earth is an oblate spheroid with a lumpy geoid, so the true figure moves by a little.
- Not a passage planIce, weather, currents and the Southern Ocean in winter are nowhere in this calculation.
“The problem was approached as a purely mathematical exercise. The authors do not recommend sailing or driving along the found paths.” Chabukswar & Mukherjee, 2018
What to notice on the map
The line isn't a route. It's a leftover.
- It touches both edgesStart and finish sit at opposite sides of the frame because the line wraps 80.1% of the way around the world. Nothing else on a world map does that without turning.
- Two needles, 9,106 km apartThe Mozambique Channel and the Drake Passage are the only tight spots. Between them the line has an entire ocean of clearance.
- It dives to miss the iceThe dip to 60°22′S isn't a detour — a straight line on a sphere has to swing that far south to clear South America and still find the Pacific.
- It ends by accidentKamchatka is not a destination. It is the first coastline that happens to stand in the way after 32,090 km of open water.