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Alright, here we go!
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 globe to look anything close to a rectangle lying flat,
I've had to cut it in several places.
I've had to stretch it so the countries are starting to look all wonky.
And even still, it's almost impossible to get it to lay 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.
That was mathematically proved, by this guy, a long time ago.
Since around 1500s,
mathematicians have set about creating algorithms that
would translate the globe into something flat.
And 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 of the
points 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 the math used by map makers to project the globe
Will effect 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 you’re American, you probably studied this map in school.
It’s the projection Google Maps uses.
The Mercator projection is popular or 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.
[Ding]
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 to the globe, you can see that this line is not shortest route.
But it provides a simple, reliable way to navigate across the ocean.
Gerardus Mercator, who created the projection in the 16th century,
was able to preserve direction by varying the distance between
the latitude lines and also making them straight.
Creating a grid of right angles.
But that created some 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 if you look at a globe for Greenland’s true size,
you’ll see it’s way smaller than Africa
By a factor of 14 in fact.
If we put a bunch of dots, on the globe, that are all the same size,
and then we projected that onto the Mercator map
we would end up with this.
The circles retain their round shape, but are enlarged
as they get closer to the poles.
One modern critique of this is that the distortion perpetuates imperialist
attitudes of European domination over the southern hemisphere
"The Mercator projection has fostered European imperialist attitudes for centuries
and created a ethnic bias against the third world."
"Really?"
So if you want to see a map that more accurately displays land area,
you can use the Gall-Peters projection,
this is called an equal-area map.
Look at Greenland and Africa now.
The size comparison is accurate.
Much better than the Mercator.
but it’s obvious now that the country shapes are totally distorted.
Here are the dots again so we 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 around the world.
[Rocket blasting off]
"Today orbiting satellites of the Navy Navigation Satellite System
provide round the clock, ultra precise position fixes, from space,
to units everywhere in any kind of weather."
This global positioning system wiped out the need for paper maps
as a means of navigating
both the seas and the sky.
Map projection choices became less about navigational imperatives and more about
aesthetics, design,and presentation
The Mercator map, that once vital tool of pre-GPS navigation,
was shunned by cartographers who
now saw it as misleading.
But even still, most web mapping tools like Google Maps, use the Mercator.
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 90 degree left turn on the street you’re driving down.
The distortion is minimal when you are close up.
But on a world map scale, cartographers rarely use the Mercator.
Most modern cartographers have settled on a
variety of non-rectangular projections that
split the difference between distorting either size or shape.
In 1998 The National Geographic Society adopted The Winkel-Tripel projection
because of it’s 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 with a new perspective on the planet.
And each useful for a different task.
The best way to see the Earth is to look at a globe.
But as long we use flat maps, we'll have to deal with the trade-offs
of projections,
And just remember:
there’s no right answer.
If you yourself want to poke fun at the Mercator projection
You can do so, by going to thetruesize.com
Which is a fun tool that allows you to drag around whatever country you want
around the map and see how it is distorted depending on where it is.
I also want to say a big thanks, to Mike Bostock
who's open source project on map projections,
was a huge help in this video.
I'll put a link to both of those things down in the description.