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

  • I’m going to have to cut it open.

  • In order to get this to look anything like a rectangle.

  • I've had to cut it in places. I've had to stretch it so that the countries look all wonky.

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

  • And that right there is the eternal dilemma of map makers: The surface of a sphere cannot

  • be represented as a plane without some form of distortion.

  • This guy proved that with math a long time ago.

  • Since around 1500s, mathematicians have set about creating algorithms that would translate

  • the globe into something flat.

  • To do this, they use a process called projection.

  • Popular rectangular maps use a cylindrical projections.

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

  • sphere onto the cylinder’s surface.

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

  • But you could also project the globe onto other objects, and how exactly a map maker

  • projects the globe will affect what the map looks like once it’s all flattened out.

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

  • shape, distance, direction and land area.

  • Certain map projections can be either misleading or very helpful depending on what you are

  • using them for.

  • Here’s an example.

  • This map is called the Mercator projection.

  • If youre American, you probably studied it in school.

  • It’s the projection Google Maps uses.

  • Mercator projection is popular for a couple of reasons.

  • First, it generally preserves the shape of the countries.

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

  • But the real purpose of the Mercator projection was navigation -- it preserves direction,

  • which is a big deal if you are trying to navigate the ocean with only a compass.

  • It was designed so that a line drawn between two points on the map would provide the exact

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

  • If we go back into a globe, you can see that this line is not shortest route.

  • But it provides a simple, reliable way to navigate across oceans.

  • Gerardus Mercator, who created the projection in the 16th century, was able to preserve

  • direction by varying the distance between latitude lines while also making them straight,

  • creating a grid of right angles..

  • But that created other problems.

  • Where mercator fails is its representation of size.

  • Look at the size of Africa as compared to Greenland.

  • On the mercator map they look about the same size.

  • But look at a globe for Greenland’s true size, and youll see it’s way smaller

  • than Africa.

  • By a factor of 14 in fact.

  • If we put some dot that are all the same size on a globe, then we projected as a mercator

  • map, we would end up with this.

  • The circles retain their shape but are enlarged the closer you get the poles.

  • One modern critique is that this distortion perpetuates imperialist attitudes of European

  • domination over the southern hemisphere

  • "The Mercator projection has fostered imperialist attitudes for centuries

  • and created a ethnic bias against the third world."

  • "Really?"

  • If you want to see a map that more accurately displays size, you can use the Gall-Peters

  • projection, which is called an equal-area map.

  • Look at Greenland and Africa.

  • The size comparison is now accurate.

  • Much better than the mercator.

  • but it’s obvious that the country shapes are now stretched.

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

  • while totally distorting shape.

  • Something happened in the late 60s that would change the whole purpose of mapping and the

  • way we think about projections.

  • Satellites orbiting our planet started sending location and navigation data to little receiver

  • units all over the world.

  • This global positioning system wiped out the need for paper maps as a means of navigating

  • both the sea and the sky.

  • Map projection choices became less about navigational imperatives and more about aesthetic design

  • and presentation.

  • The mercator map, that vital tool of pre-GPS navigation, was shunned by cartographers who

  • now saw it as misleading.

  • But most web mapping tools like Google maps still use the mercator.

  • According to Google this is because the Mercator’s ability to preserve shape and angles makes

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

  • left turn on the street youre driving down.

  • But when trying to display something on a world map, cartographers rarely use the mercator.

  • Most modern cartographers have settled on a variety of non-rectangular projections that

  • split the difference between totally distorting either size or shape.

  • In 1998 The National Geographic Society adopted The Winkel tripel projection because of it’s

  • a pleasant balance between size and shape accuracy.

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

  • cartographers and mathematicians have created a huge library of available projections, each

  • a new perspective on the planet.

  • The best way to see what the earth really looks like is to look at a globe.

  • But as long we use flat maps, we will deal with the tradeoffs of projections, Just remember:

  • there’s no right answer.

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

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B1 中級 美國腔

為什麼世界地圖都是錯的 (Why all world maps are wrong)

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    liufei 發佈於 2021 年 01 月 14 日
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