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♪

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Alright, here we go!

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If I want to turn this globe [br]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 [br]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 [br]countries are starting to look all wonky.

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

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And that right there is the eternal [br]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[br]of distortion.

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

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Since around 1500s,

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mathematicians have set about[br]creating algorithms that

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would translate the globe [br]into something flat.

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

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Popular rectangular maps use a cylindrical[br]projections.

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

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points of the sphere onto [br]the cylinder’s surface.

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

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But you could also project the globe onto[br]other objects,

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and the math used by map makers [br]to project the globe

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

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And here’s the big problem: Every one of[br]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 [br]be either misleading

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or very helpful [br]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 [br]Mercator projection.

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

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It’s the projection Google Maps uses.

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The Mercator projection is popular [br]or a couple of reasons.

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First, it generally preserves the [br]shape of the countries.

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Brazil on the globe has the same shape as[br]Brazil on the Mercator projection.

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[Ding]

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But the real purpose of the Mercator[br]projection was navigation --

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

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trying to navigate[br]the ocean with only a compass.

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It was designed so that a line drawn [br]between two points

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on the map [br]would provide the exact

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angle to follow on a compass to [br]travel between those points.

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

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

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Gerardus Mercator, who created the [br]projection in the 16th century,

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was able to preserve direction [br]by varying the distance between

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the latitude lines [br]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[br]of size.

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Look at the size of Africa[br]as compared to Greenland.

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On the Mercator map they look [br]about the same size.

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

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you’ll see it’s way [br]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, [br]that are all the same size,

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and then we projected that [br]onto the Mercator map

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we would end up with this.

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The circles retain their round shape, [br]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 [br]distortion perpetuates imperialist

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attitudes of European domination [br]over the southern hemisphere

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"The Mercator projection has fostered [br]European imperialist attitudes for centuries

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and created a ethnic bias [br]against the third world."

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"Really?"

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So if you want to see a map that more [br]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 [br]shapes are totally distorted.

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Here are the dots again so we can see how[br]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 [br]purpose of mapping

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and the way we think about projections.

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Satellites orbiting our planet started [br]sending location and navigation data

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to little receiver units all [br]around the world.

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[Rocket blasting off]

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"Today orbiting satellites of the [br]Navy Navigation Satellite System

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provide round the clock, ultra precise [br]position fixes, from space,

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to units everywhere in [br]any kind of weather."

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This global positioning system [br]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 [br]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 [br]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 [br]like Google Maps, use the Mercator.

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

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

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

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The distortion is minimal when [br]you are close up.

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

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Most modern cartographers have [br]settled on a

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variety of non-rectangular [br]projections that

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split the difference between distorting[br]either size or shape.

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In 1998 The National Geographic Society [br]adopted The Winkel-Tripel projection

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because of it’s pleasant balance

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between size and shape[br]accuracy.

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

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Cartographers and mathematicians have [br]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[br]is to look at a globe.

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But as long we use flat maps, [br]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 [br]the Mercator projection

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You can do so, [br]by going to thetruesize.com

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

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

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I also want to say a big thanks, [br]to Mike Bostock

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who's open source project [br]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 [br]down in the description.