WEBVTT

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♪

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Alright, here we go!

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If I want to turn this globe 
into a flat map,

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I’m going to have to cut it open.

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In order to get this globe to look 
anything close to a rectangle lying flat,

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I've had to cut it in several places.

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I've had to stretch it so the 
countries are starting to look all wonky.

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And even still, it's almost impossible 
to get it to lay flat.

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And that right there is the eternal 
dilemma of map makers.

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The surface of a sphere cannot be

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represented as a plane without some form
of distortion.

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That was mathematically proved,
by this guy, a long time ago.

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Since around 1500s,

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mathematicians have set about
creating algorithms that

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would translate the globe 
into something flat.

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And to do this, they use a 
process called projection.

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Popular rectangular maps use a cylindrical
projections.

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Imagine putting a theoretical cylinder
over the globe and projecting each of the

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points of the sphere onto 
the cylinder’s surface.

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Unroll the cylinder, and you have a flat,
rectangular map.

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But you could also project the globe onto
other objects,

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and the math used by map makers 
to project the globe

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Will effect what the map
looks like once it’s all flattened out.

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And here’s the big problem: Every one of
these projections comes with trade offs in

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shape, distance, direction and land area.

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Certain map projections can 
be either misleading

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or very helpful 
depending on what

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you are using them for.

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Here’s an example.

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This map is called the 
Mercator projection.

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If you’re American, you probably studied 
this map in school.

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It’s the projection Google Maps uses.

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The Mercator projection is popular 
or a couple of reasons.

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First, it generally preserves the 
shape of the countries.

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Brazil on the globe has the same shape as
Brazil on the Mercator projection.

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[Ding]

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But the real purpose of the Mercator
projection was navigation --

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it preserves direction,
which is a big deal if you are

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trying to navigate
the ocean with only a compass.

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It was designed so that a line drawn 
between two points

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on the map 
would provide the exact

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angle to follow on a compass to 
travel between those points.

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If we go back to the globe, you can 
see that this line is not shortest route.

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But it provides a simple, reliable way to
navigate across the ocean.

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Gerardus Mercator, who created the 
projection in the 16th century,

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was able to preserve direction 
by varying the distance between

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the latitude lines 
and also making them straight.

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Creating a grid of right angles.

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But that created some other problems.

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Where Mercator fails is its representation
of size.

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Look at the size of Africa
as compared to Greenland.

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On the Mercator map they look 
about the same size.

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But if you look at a globe for 
Greenland’s true size,

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you’ll see it’s way 
smaller than Africa

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By a factor of 14 in fact.

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If we put a bunch of dots, on the globe, 
that are all the same size,

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and then we projected that 
onto the Mercator map

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we would end up with this.

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The circles retain their round shape, 
but are enlarged

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as they get closer to the poles.

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One modern critique of this is that the 
distortion perpetuates imperialist

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attitudes of European domination 
over the southern hemisphere

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"The Mercator projection has fostered 
European imperialist attitudes for centuries

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and created a ethnic bias 
against the third world."

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"Really?"

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So if you want to see a map that more 
accurately displays land area,

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you can use the Gall-Peters projection,

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this is called an equal-area map.

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Look at Greenland and Africa now.

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The size comparison is accurate.

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Much better than the Mercator.

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but it’s obvious now that the country 
shapes are totally distorted.

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Here are the dots again so we can see how
the projection preserves area

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while totally distorting shape.

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Something happened in the late 60s

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that would change the whole 
purpose of mapping

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and the way we think about projections.

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Satellites orbiting our planet started 
sending location and navigation data

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to little receiver units all 
around the world.

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[Rocket blasting off]

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"Today orbiting satellites of the 
Navy Navigation Satellite System

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provide round the clock, ultra precise 
position fixes, from space,

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to units everywhere in 
any kind of weather."

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This global positioning system 
wiped out the need for paper maps

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as a means of navigating

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both the seas and the sky.

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Map projection choices became less about 
navigational imperatives and more about

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aesthetics, design,and presentation

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The Mercator map, that once vital tool of 
pre-GPS navigation,

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was shunned by cartographers who

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now saw it as misleading.

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But even still, most web mapping tools 
like Google Maps, use the Mercator.

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This is because the Mercator’s
ability to preserve shape and angles makes

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close-up views of cities more accurate -- 
a 90 degree left turn on the map

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is a 90 degree left turn on 
the street you’re driving down.

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The distortion is minimal when 
you are close up.

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But on a world map scale, 
cartographers rarely use the Mercator.

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Most modern cartographers have 
settled on a

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variety of non-rectangular 
projections that

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split the difference between distorting
either size or shape.

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In 1998 The National Geographic Society 
adopted The Winkel-Tripel projection

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because of it’s pleasant balance

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between size and shape
accuracy.

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But the fact remains, that there is 
no one right projection.

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Cartographers and mathematicians have 
created a huge library

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of available projections.

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Each with a new perspective on the planet.

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And each useful for a different task.

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The best way to see the Earth
is to look at a globe.

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But as long we use flat maps, 
we'll have to deal with the trade-offs

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of projections,

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And just remember:

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there’s no right answer.

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If you yourself want to poke fun at 
the Mercator projection

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You can do so, 
by going to thetruesize.com

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Which is a fun tool that allows you to 
drag around whatever country you want

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around the map and see how it 
is distorted depending on where it is.

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I also want to say a big thanks, 
to Mike Bostock

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who's open source project 
on map projections,

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was a huge help in this video.

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I'll put a link to both of those things 
down in the description.