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How do Map Projections Work?
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Mar 31, 2025
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0:00
Maps. They are attempts at representing our countries and continents on a flat surface
0:08
To follow the Wikipedia definition, in cartography, a map projection is a way to flatten a globe's
0:15
surface into a plane in order to make a map. But there's an issue. It's impossible to do it in a
0:21
way that is 100% accurate, because we need to transform latitude and longitude lines from the
0:28
globe into locations on a plane surface. A lot of times people use an orange peel to explain this
0:34
issue. If you peel an orange, you can't flatten it out on a table without messing the peel up
0:40
And so all projections of a sphere on a plane necessarily distort the surface in some way and
0:46
to some extent in order for all of it to be present. This is why we have a lot, and when I say a lot
0:52
I mean a lot of map projections, just searching for this video, I found around 250 and they are
0:58
virtually infinite because depending on the purpose of the map, some distortions are acceptable
1:04
and others are not. Therefore, different map projections exist and are created in order to
1:10
preserve some properties of the sphere-like body that is the earth at the expense of others being
1:17
distorted. They can belong to seven groups, but I'm going to try to not get too technical here
1:22
especially because I have very little idea about the technicalities and mostly go at it from a
1:27
visual perspective. The most well-known map projection used in the majority of maps across
1:32
the world is the Mercator projection presented by Flemish geographer and cartographer Gerardus
1:38
Mercator in 1569. It's pretty old and its generalized use has to do with the date in which
1:45
it was invented. These were the times of the European colonialism and maritime discoveries
1:50
And so, this map focused on representing any constant course of constant bearing of a ship as a straight segment on the map
1:59
To put it simply, if in order to get from southern France to Canada, your ship had to just go forward and never turn
2:05
then the map would show a straight line between the two locations. And so, this projection became the standard map for navigation
2:13
However, it has a big issue. The Mercator projection inflates the sizes of objects away from the equator
2:19
This inflation is very small near the equator, allowing countries and continents there to be
2:24
represented very accurately, but becomes distorted being too big as it moves towards the poles
2:30
In this GIF, yes, GIF, not JIF, we can see countries being reduced to their true size
2:36
The ones near the equator have little to no change, while the ones up north shrink a lot
2:42
Greenland appears to be the size of Africa, when in reality, it is 14 times smaller
2:47
Madagascar looks the same size as the UK when in fact it is twice its size
2:53
Alaska seems to be the same size as Brazil when Brazil is five times bigger
2:58
Antarctica looks gigantic when in reality it is reasonably small. It's just at the southern pole and so is reachable on a globe from all surrounding areas depicted here on the southern part of the map
3:11
And so in order to depict that reachability the map must show it distorted like this I made a video about this specific issue once regarding the true size of countries Eventually the Mercator projection has become a little less used
3:25
although I think it's still the one in the majority of maps, but a lot of them switched
3:29
to better ones, which are more accurate. A good example and one extremely used nowadays
3:35
is the Robinson projection, developed in 1987 and adopted by the US's National Geographic
3:42
Society in 1988 as their official projection. Before that, they used the Van der Grinten
3:48
projection, which reduced Mercator's distortion in the center by concentrating all of it in the
3:53
poles, which were extremely distorted, representing the globe as a circle. The Robinson projection
3:59
almost solves it entirely though, and is honestly my favorite one because of this
4:03
The distortion in size is basically non-existent, and only the actual poles are distorted
4:09
like we see with Antarctica, but something which I think is justified with the necessity of showing
4:14
its accessibility from all areas of the South-Southern Hemisphere. An interesting aspect
4:19
in the majority of these projections is that the distortion is usually horizontally symmetric
4:25
from the equator line. I'm sure there's some mathematic reason behind that. The Berman
4:29
projection from 1910, for instance, shows a really weird-looking Central America, South America
4:35
and Africa, they are way too disproportionately big when compared to North America, Europe
4:41
and most of Asia. But they are disproportionate in a symmetrical way
4:45
So now we've understood three things. 1. All maps are distorted because it's impossible to depict a globe on a flat surface. 2
4:54
The type of distortion the map has depends on what it was made for
4:58
The Mercator projection was made for ship traveling and so it prioritizes that, the courses
5:03
and directions. sacrificing object proportions in some parts of the map. And three other maps have since tried to
5:11
correct those errors in distortion, either prioritizing other aspects or attempting to
5:16
depict our continents in the most accurate way possible on a flat surface. This is why there are
5:22
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6:32
All these maps we seen so far have been however pretty standard and straightforward in the sense that they are the way we expect a map to look like But what about all the other projections that look way different Let start with this one
6:45
This is the transverse Mercator. Essentially, it stems from the Mercator projection, but depicts it in a different shape slash angle
6:53
Now, again, I'm totally ignorant regarding the math behind this, but it's in the math
6:57
that the difference is, and that's something out of my area of expertise
7:01
But there is the obvious difference in the visual aspect. Here, the pole's sizes are pretty much near perfection, but other areas suffer as a consequence
7:10
Southeast Asia is way too big, as is South America, but Antarctica is perfectly depicted
7:16
So, if we were to use the two Mercator projections side by side, we would have an almost perfect depiction of our world
7:25
We also have examples of maps which didn't have to deal with Antarctica's problem because, well, when they were made, Antarctica hadn't been discovered yet
7:32
Lambert's conformal conic projection from 1772 is a good example of this and
7:38
it's actually extremely proportionate in pretty much every aspect, although it is missing the tips of South America, South Africa, Australia and New Zealand
7:48
entirely. This map projection is apparently still the basis for a lot of
7:52
the aeronautical charts used by air pilots because a straight line drawn on
7:57
a Lambert conformal conic projection approximates a great circle root between two points for
8:04
flight distances. What we therefore understand is that essentially when cartographers and geographers develop
8:10
these map projections, they always come up with specific mathematical principles behind them
8:16
And these principles can still be used today, even if the original map projection itself
8:21
is not, because it became outdated. That's why the amount of map projections is virtually infinite, because we can always
8:28
change something in a projections equation, even if a tiny detail, or come up with an
8:33
entirely new projection. Another example of a perhaps outdated projection is the stereographic projection
8:40
All of these have really complicated and technical names that I don't understand either, so the
8:45
best way to understand them is by seeing how they look. This one is also known as a planisphere projection and it dates back to antiquity, having been
8:53
used in some of ancient Greece and Rome's maps. Depicted on a circle, instead of being centered on the equator, it is centered on the north
9:01
pole with an increased level of distortion as you move away from it
9:05
But the errors were excusable because the point was to depict the northern hemisphere
9:10
with a high level of accuracy. However, some more recent projections just wanted to depict all continents with the minimal
9:17
error possible. An example of that is the Aerie minimum error projection, which pretty much took the globe
9:23
cut it in half and put two circles side by side. Some follow the same trend and use two different
9:29
surfaces put together like Van Leeuwen's GC which uses two triangles or Adam's hemispheres which
9:38
uses two Lozangs. This circle one is very accurate but still not perfect because it's not possible
9:43
to demonstrate the curvature of the globe in the central part of the circle and so these areas here
9:49
Russia the Central Asia Istans or India are a little too far stretched when compared with Italy or Ireland over there We could stay here for hours just looking at map projections but I think at this point we understood the basic principles behind them and why they are so
10:05
different and vary so much. Like a projection proposed by Leonardo da Vinci in 1508, which
10:11
set the path for Cahill's butterfly projection by attempting to divide the globe into eight pieces
10:18
So I'm just going to show you two or three more that I found really cool looking and that are
10:22
amongst the most unique out of the currently existing models. First, the one I just mentioned
10:28
which comes from Leonardo da Vinci's ideas, the Cahill conformal butterfly. In it, we see the
10:33
world depicted in eight triangles. And honestly, it might not be in the orientation we're used to
10:39
or in a rectangular depiction, but I kind of love it. Look at the accurateness of the sizes
10:44
the precise depiction of Antarctica's reachability without having to stretch it to no end
10:49
It's just totally brilliant. Plus, the issue we have of certain continents being split
10:54
can be solved by moving the triangles according to our desire. These are visible in other forms
11:01
of arranging this projection, like the Cahill conformal M-shaped. There's also the Cahill
11:06
Keys projection, which depicts the world also in eight triangular shapes, although one of them has
11:11
an additional piece for Antarctica. There is also a cool one called the Cheselange conformal. The
11:17
name I guess comes from the fact that it looks like one. It's pretty good and despite not looking
11:21
like it because it's separated, it shows us the entire world very accurately. However, I feel the
11:27
way of dividing it isn't the best because it takes away our notion of distance and if we didn't have
11:32
pre-existing knowledge of where things are in relation to each other, it would be kind of
11:37
useless in terms of serving its purpose as a map. Then the De Maxion-like conformal from 1943
11:44
which attempts to transform the sphere into an icosahedron, a shape with 20 sides
11:51
then flattening out those 20 sides on a surface. It preserves shapes and sizes very well, but is heavily interrupted as a consequence
12:00
But to be fair, I think at this point, the goal of the makers wasn't to create a useful map
12:05
in the sense of it being good for navigating via sea, land, or air
12:09
They were or are just trying to make the most accurate depiction of a globe on a flat surface
12:15
And finally, the Schierning I from 1982, which I just find extraordinary because it really takes
12:23
the whole stretched Antarctica thing to a max. It depicts the world in a semicircle being centered
12:28
on the top center in the North Pole and having the Southern Pole stretched all around its limits
12:35
So, that is a quick overview of map projections. Why they exist, why they are all necessarily inaccurate, how some of them prioritize depicting
12:44
some aspects correctly and others not, depending on what they were made for, and how some of
12:49
them have attempted to be the most accurate possible. There's literally hundreds of other projections, but I couldn't fit them all into a video
12:56
with an acceptable length, so if you're interested in this, just Google it and you'll find endless
13:01
information on it. Thanks so much for watching this video. subscribe if you want to and leave a comment below with your favorite map projection
13:09
I will see you next time for more general knowledge
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