Perceptions and Projections – a Mapping story

When you reduce a 3D object to a 2D map you are bound to distort and lose some data in the process. Our perceptions are often influenced by what data is chosen to be retained and what is chosen to be lost. And this could influence our decisions

Take the world map for instance.

Earth is an oblate ellipsoid approximated to a sphere. On a globe, it would be natural to follow a spherical coordinate system. This leads us to draw longitudes and latitudes for convenience.

spherical coordinate

If you’re like Flemish cartographer Gerardus Mercator in 1569 and you want to draw a map for the purposes of navigation, you’d consider drawing those longitude and latitude curves as parallel lines on flat paper – to help your nautical buddies map their route better with lines of constant course.

long lat globe

mercator long lat

That’s your standard map – the one we’re all familiar with, the one used to drill geography into little kid’s heads, the one used by global decision makers – the Mercator projection – the map on which we imagine the world. This becomes our constructed reality.

On a globe Africa is around 14 times larger than Greenland. South America is almost double the size of Europe. Brazil is 5 times the size of Alaska. Don’t believe me, go check a globe. The Mercator map distorts relative sizes.

deformation at pole

Without getting into the mathematics of it, in the Mercator map, as we move away from the equator, distance between two points on a globe is stretched further when projected on this 2D map. Since Greenland is closer to the pole, it is quite significantly stretched. That is why Greenland looks as if it is the same size as Africa even though Africa is 14 times large as it!

gall peters

The Gall-Peters projection does a cylindrical equal area map projection – conserving relative sizes. An equal area map such as this distorts shapes.

How does this influence perception? Some say the Mercator map depicts a European imperialist attitude. Europe lies at the top and occupies quite a lot of space in the Mercator projection. We unconsciously associate size with importance and power. Would we think about world issues differently – increasing desertification or a poor standard of living in Africa –with a Gall-Peters view of the world?

Furthermore, convention has distorted our perception of reality. Consider the following:

gall peters

is as real as

gall peters 2

 

Which is the best projection? They all have some kind of distortion, so the answer depends on which kind of distortion does the least harm for our purposes, and is convenient.

types of projections

At a more micro level, could the way maps are drawn affect us on a daily basis? Possibly!
Professor Zhan Guo has studied how maps influence decisions concerning which path to take. The Tube map shows schematic relative positions rather than exact geographical locations – and in doing so distorts distances. The correlation between actual distance and transit map distance was found to be just 0.22! According to him the London Tube map ‘has a tremendous impact on passenger’s perceptions and his or her usage of the transit system’ since ‘passengers trust the Tube map more than their own travel experience on deciding the ‘best’ travel path.’ This bias makes it likely to take a longer path if it is perceived as being shorter in the map.

tube_map

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The underlying point is  that some of what we perceive of the world is a constructed reality. And this constructed reality influences our choices to some extent.

Don’t be so sure of what you perceive as reality. Question perceptions and conventions.

Keep questioning!

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Suggestion : Use the inverted Gall-Peters projection map as your desktop wallpaper for a while, you may begin to picture the world differently.

Check out Randall Munroe’s take on the different map projections : https://xkcd.com/977/

Images and information from Wikipedia

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