00:00all right here we go if I want to turn this globe into a flat map I'm gonna have to cut it open
00:08in order to get this globe to look anything close to a rectangle lying flat I've had to cut it in
00:22several places I've had to stretch it so that the countries are starting to look all wonky and even
00:28still it's almost impossible to get it to lay flat and that right there is the eternal dilemma of
00:36map makers the surface of a sphere cannot be represented as a plane without some form of
00:42distortion that was mathematically proved by this guy a long time ago since around the 1500s
00:47mathematicians have set about creating algorithms that would translate the globe into something flat
00:52and to do this they use a process called projection popular rectangular maps use a cylindrical
00:58projection imagine putting a theoretical cylinder over the globe and projecting each of the points
01:03of the sphere onto the cylinder surface unroll the cylinder and you have a flat rectangular map but
01:11you could also project the globe onto other objects and the math used by map makers to project the globe
01:16will affect the way the map looks once it's all flattened out and here's the big problem every one
01:23of these projections comes with trade-offs in shape distance direction and land area certain map
01:28projections can either be misleading or very helpful depending on what you're using them for here's an
01:34example this map is called the Mercator projection if you're American you probably studied this map in
01:40school it's also the projection that Google Maps uses the Mercator projection is popular for a couple of
01:45reasons first it generally preserves the shape of countries Brazil on the globe has the same shape as Brazil on the Mercator
01:52projection but the original purpose of the Mercator projection was navigation it preserves direction
01:59which is a big deal if you're trying to navigate the ocean with only a compass it was designed so
02:04that a line drawn between two points on the map would provide the exact angle to follow on a compass
02:09to travel between those two points if we go back to the globe you can see that this line is not the shortest
02:15route but at least it provides a simple reliable way to navigate across the ocean Gerardus Mercator who
02:21created the projection in the 16th century was able to preserve direction by varying the distance
02:26between the latitude lines and also making them straight creating a grid of right angles but that
02:33created some other problems where the Mercator fails is its representation of size look at the
02:38size of Africa as compared to Greenland on the Mercator map they look about the same size but if you
02:43look at a globe for Greenland's true size you'll see that it's way smaller than Africa by a factor of 14 in
02:49fact if we put a bunch of dots onto the globe that are all the same size and then project that onto the
02:56Mercator map we will end up with this the circles retain their round shape but are enlarged as they get
03:03closer to the poles one modern critique of this is that the distortion perpetuates imperialist attitude of
03:08European domination over the southern hemisphere okay the Mercator projection has fostered European
03:14imperialist attitudes for centuries and created an ethnic bias against the third world really so if
03:20you want to see a map that more accurately displays land area you can use the gall peters projection this
03:25is called an equal area map look at Greenland and Africa now the size comparison is accurate much
03:31better than the Mercator but it's obvious now that the country shapes are totally distorted here are those dots
03:37again so that we can see how the projection preserves area while totally distorting shape something
03:45happened in the late 60s that would change the whole purpose of mapping in the way that we think about
03:50projections satellites orbiting our planet started sending location and navigation data to little
03:55receiver units all around the world today orbiting satellites of the Navy navigation satellite system provide
04:03round-the-round-the-clock ultra precise position fixes from space to units everywhere in any kind of
04:10weather this global positioning system wiped out the need for paper maps as a means of navigating both
04:17the sea and the sky map projection choices became less about navigational imperatives and more about
04:23aesthetic design and presentation the Mercator projection that once vital tool of pre-GPS navigation was shunned by
04:31cartographers who now saw it as misleading but even still most web mapping tools like Google Maps use the Mercator
04:38this is because the Mercator's ability to preserve shape and angles makes close-up views of cities more
04:44accurate a 90 degree left turn on the map is a 90 degree left turn on the street that you're driving down
04:49the distortion is minimal when you're close up but on a world map scale cartographers rarely use the Mercator
04:56most modern cartographers have settled on a variety of non rectangular projections that
05:01split the difference between distorting either size or shape in 1998 the National Geographic Society
05:07adopted the Winkle triple projection because of its pleasant balance between size and shape
05:12accuracy but the fact remains that there's no right projection cartographers and mathematicians
05:17have created a huge library of available projections each with a new perspective on
05:22the planet and each useful for a different task the best way to see the earth is to look at a globe but
05:28as long as we use flat maps we'll have to deal with the trade-offs of projections and just remember
05:33there's no right answer if you yourself want to poke fun at the Mercator projection you can do so by
05:41going to the true size of dot-com which is a fun tool that allows you to drag around whatever country
05:47you want around the map and see how it is distorted depending on where it is I also want to say a big
05:52thanks to Mike Bostock whose open source project on map projections was a huge help in this video
05:57I'll put a link for both of those things down in the description
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