Spilhaus projection
The Spilhaus projection flips traditional cartographic priorities: instead of continuous landmasses, it preserves the integrity of the world ocean. It is an oblique map in a square where continents are torn apart to frame a single, connected body of water.
The world from the perspective of fish and ocean currents
The geophysicist and oceanographer Athelstan Spilhaus worked on ocean maps from 1942 and published this square version in 1979. It changes how we perceive the Earth. Traditional projections sever the oceans at the map borders (such as dividing the Pacific), complicating the study of ocean currents. Spilhaus moved the cuts onto land, splitting Asia and both Americas, to show a globally connected water system centered on Antarctica.
Mathematically, it builds on an oblique aspect of the conformal Adams World in a Square II projection. As a conformal map, local shapes of islands and coastlines are accurately preserved. The side effect, however, is massive size distortion for landmasses located near the square's margins (like Asia or North America), which are stretched to colossal proportions.
Global Cartographic Grid
Distortion Properties
| Property | Characteristic |
|---|---|
| Area | DistortedHighly distorted: the conformal projection greatly enlarges land near the edges and corners of the square (on our map especially Argentina, China, Canada, and the USA) |
| Shape | PreservedPreserved locally (conformal), except at the four corners of the square |
| Distances | DistortedDistorted across the globe; scale varies greatly between the center and the edges of the square |
| Angles and directions | PreservedPreserved locally (conformal), except at the four corners of the square |
| Continuity | InterruptedInterrupted on land: the edge of the square cuts through Asia and North and South America, while the world ocean stays continuous |
History & Origin
The South African-American geophysicist and oceanographer Athelstan Spilhaus was already looking for a way to show the world ocean as a single, continuous body of water in 1942, to make marine currents easier to visualize. He published the square map now known as the Spilhaus projection in 1979, with the help of Robert Hanson and Ervin Schmid of the U.S. National Geodetic Survey. It is an oblique aspect of the conformal Adams World in a Square II projection from 1925, rotated so the cuts run through land and Antarctica sits near the center.
Applications
Visualizing ocean currents, water temperature and salinity, the spread of marine pollution, and migration patterns of marine life. An invaluable tool in oceanography and aquatic ecosystem education.
How to read this map
Imagine viewing the Earth from the bottom (the South Pole) and pulling the continents apart like curtains toward the edges of a square screen, leaving the ocean intact in the middle.
- Locate Antarctica near the center of the map. It represents the heart of the world ocean.
- Trace a sea route from Africa to America; you will see it is completely uninterrupted.
- Find Russia, Canada, and China. The edge of the square cuts them, and Canada and China are strongly enlarged next to it.
- Use this map to analyze global ocean circulation, not to compare the sizes of nations.
What you gain and lose
Spilhaus sacrifices land continuity and area proportions to achieve absolute ocean continuity on a conformal square grid.
Oceanographic maps, illustrating climate change, ocean currents, marine migration, and lessons on geocurrent biases.
Political maps, land navigation, and teaching about continental areas.
Not sure this projection fits your map? Answer three questions in the finder →
Want to see it next to another projection? Compare: Spilhaus Projection vs Mercator →
Can you recognize this projection without the label?
The projection quiz uses graticules and world outlines, so it is a natural next step from this page.
One attempt, the same set for everyone
Size illusion · Build a streak and come back tomorrow for another map.
✦ How do different countries look in this projection?
Analyze shape distortions of 5 countries in this cartographic projection and test them in the sandbox.
Poland is not cut, but it lies far from the center and looks much smaller than countries near the edges, which illustrates how the projection treats Europe.
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The United States lies on the periphery, with its Pacific and Atlantic coasts positioned extremely far apart.
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Australia sits close to the oceanic center, maintaining a relatively faithful shape in the conformal grid.
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Brazil stays whole and forms part of the Atlantic's frame, while neighboring Peru and Argentina are cut by the map edge.
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South Africa sits at a key junction connecting the Atlantic and Indian oceans without any interruption.
Test on map →Facts worth remembering
- Athelstan Spilhaus was a distinguished geophysicist and inventor, famous for the bathythermograph used to measure deep-sea temperatures.
- The projection was popularized again in 2018 by developers and cartographers working with modern GIS tools.
- The North Pole is a single point near the top edge of the square, and the center of the map lies in the southern Indian Ocean.
Keep reading about maps that reshape intuition
Frequently Asked Questions
It is primarily used for oceanography and studying the seas. In this map, all of Earth's oceans form a single, continuous body of water, making it easier to analyze marine currents and global climate systems.
This is intentional. In order to keep the world ocean continuous on a flat sheet, Spilhaus shifted all cartographic cuts onto landmasses, splitting North America, South America, and Asia.
The center of the map lies in the southern Indian Ocean, with Antarctica right next to it. The North Pole is a single point near the top edge of the square.
No, it is a conformal (equal-angle) projection. It preserves local shapes and angles but heavily exaggerates the areas of landmasses positioned near the edges of the square.
Countries near the edges and corners of the square, where enlargement peaks: on our map especially Argentina, China, Canada, and the USA. Some of them, and also Russia, Mexico, and Peru, are cut by the map edge as well.