How do Map Projections Work?

Maps they are attempts at representing our countries and continents on a flat surface to follow the Wikipedia definition in cartography a map projection is a way to flatten a globe's surface into a plane in order to make a map but there's an issue it's impossible to do it in a way that is 100% accurate because we need to transform latitude and longitude lines from the globe into locations on a plane surface a lot of times people use an orange peel to explain this issue if you peel an orange you can't flatten it out on a table without messing the peel up and so all projections of a sphere on a plane necessarily distort the surface in some way and 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 I mean a lot of map projections just searching for this video I found around 250 and they are virtually infinite because depending on the purpose of the map some distortions are acceptable and others are not therefore different map projections exist and are created in order to preserve some properties of the sphere like body that is the earth at the expense of others being distorted they can belong to seven groups but I'm going to try to not get too technical here especially because I have very little idea about the technicalities and mostly go at it from a visual perspective the most well-known map projection used in the majority of maps across the world is the Mercator projection presented by Flemish geographer and cartographer Gerardo's market or in 1569 it's pretty old and it's generalized use has to do with the date in which it was invented these were the times of the European colonialism and maritime discoveries and so this map focused on representing any constant course of constant bearing of a ship as a straight segment on the map to put it simply if in order to get from southern France to Canada your ship had to just go forward and if returned then the map would show a straight line between the two locations and so this projection became the standard map for navigation however it has a big issue humor couture projection inflates the sizes of objects away from the equator this inflation is very small near the equator allowing countries and continents there to be represented very accurate but becomes distorted being too big as it moves towards the poles in this gif yes gif not Jeff we can see countries being reduced to their true size the ones near the equator have little to no change while the ones up north shrink a lot Greenland appears to be the size of Africa when in reality it is 14 times smaller Madagascar looks the same size as the UK when in fact it is twice its size Alaska seems to be the same size as Brazil when Brazil is 5 times bigger and tarda girl 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 and so in order to depict that reach ability the map must show it distorted like this I made a video about this specific as she wants regarding the true size of countries eventually the Mercator projection has become a little less used although I think it's still the one in the majority of maps but a lot of them switched to better ones which are more accurate a good example and one extremely used nowadays is the Robinson projection developed in 1987 and adopted by the USS National Geographic Society in 1988 as their official projection before that they used the van der green 10 projection which reduced marketer's distortion in the centre by concentrating all of it in the poles which were extremely distorted representing the globe as a circle the Robinson projection almost solves it entirely though and is honestly my favorite one because of this the distortion in size is basically non-existent and only the actual poles are distorted like we see with Antarctica but something which i think is justified with the necessity of showing its accessibility from all areas of the south southern hemisphere an interesting aspect in the majority of these projections is that the distortion is usually horizontally symmetric from the equator line I'm sure there's some mathematic reason behind that the Behrman projection from 1910 for instance shows a really weird-looking Central America South America and Africa they are way too disproportionately big when compared to North America Europe and most of Asia but they are disproportionate in a symmetrical way so now we've understood three things one all maps are distorted because it's impossible to depict a globe on a flat surface to the type of distortion the map has depends on what it was made for the Mercator projection was made for ship traveling and so it prioritizes that the courses and directions sacrificing object proportions in some parts of the map and three other maps have since try to correct those errors in distortion either prioritizing other aspects or attempting to depict our continents in the most accurate way possible on a flat surface this is why there are so many projections before we go on with the video a quick message about today's sponsor expressvpn whenever we are online were divulging information either we are aware of it by for instance sending someone a message or were not and websites we visit retrieve it from us without us knowing they do like information about you your IP address or location plus your internet service provider knows everything you do as well expressvpn puts a stop to all of that by encrypting your data and hiding your location this way hackers websites and service providers can't access your data and use it for negative things plus you also get the added benefit of being able to visit websites that are geo restricted I recently wanted to watch the office on Netflix but that isn't available where I live and using expressvpn allowed me to switch my region to the u.s. accessing their catalog and watching the show find out how you can get three months free by clicking the link in the description box below expressvpn comm / general knowledge all these maps we've seen so far have been however really standard and straightforward in the same that they are the way we expect a map to look like but what about all the other projections that look way different let's start with this one this is the transverse Mercator essentially it stems from the market or projection but depicted in a different shape / angle now again I'm totally ignorant regarding the math behind this but it's in the math that the difference is and that's something out of my area of expertise but there is the obvious difference in the visual aspect here the pole sizes are pretty much near perfection but other areas suffer as a consequence Southeast Asia is way too big as is South America but Antarctica is perfectly depicted so if we were to use the to market world projections side-by-side we would have an almost perfect depiction of our world 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 Lambert's conformal conic projection from 1772 is a good example of this and 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 entirely this map projection is apparently still the basis for a lot of the aeronautical charts used by air pilots because a straight line drawn on a lambert conformal conic projection approximates a great circle route between two points for flight distances what we therefore understand is that essentially when cartographers and geographers develop these map projections they always come up with specific mathematical principles behind them and these principles can still be used today even if the original map projection itself is not because it became outdated that's why the amount of map projections is virtually infinite because we can always change something in a projections equation even if a tiny detail or come up with an entirely new projection another example of a perhaps outdated projection is the stereographic projection all of these have really complicated and technical names that I don't understand either so the best way to understand them is by seeing how they look this one is also known as a planisphere section and it dates back to antiquity haven't been used in some of ancient Greece and Rome maps depicted on a circle instead of being centered on equator it is centered on the North Pole with an increased level of distortion as you move away from it but the errors were excusable because the point was to depict the northern hemisphere with a high level of accuracy however some more recent projections just wanted to depict all continents with a minimal error possible an example of that is the airy minimum error projection which pretty much took the globe cut it in half and put two circles side-by-side some follow the same trend and used two different surfaces put together like Van Lee weapons GC which uses two triangles or Adams hemispheres which uses two law Zhang's this circle one is very accurate but still not perfect because it's not possible to demonstrate the curvature of the globe in the central part of the circle and so these areas here Russia the Central Asia astons or India are a little too far stretched when compared with Italy or Island over there we could stay here for hours just looking at map projections but I think at this point we've understood the basic principles behind them and why they are so different and very so much like a projection proposed by Leonardo da Vinci in 1508 which set the path for Cahill's butterfly projection by attempting to divide the globe into eight pieces so I'm just going to show you two or three more that I found really cool looking and that are amongst the most unique out of the currently existing models first the one I just mentioned which comes from Leonardo da Vinci's ideas the cahill conformal butterfly in a true CD world depicted in eight triangles and honestly it might not be in the orientation were used to or in a rectangular depiction but I kind of love it look at the accurateness of the sizes the precise depiction of Antarctica's reach ability without having to stretch it in a wind it's just totally brilliant plus the issue we have of certain continents being split can be solved by moving the triangles according to our desire these are visible in other forms of arranging this projection like the cahill conformal MA there's also the K Hokies projection which depicts the world also in eight triangular shapes although one of them has an additional piece for Antarctica there is also a cool one called the shez launched conformal the name i guess comes from the fact that it looks like one it's pretty good and despite not looking like it because it's separated it shows us the entire world very accurately however i feel the way of dividing it isn't the best because it takes away our notion of distance and if we didn't have pre-existing knowledge of where things are in relation to each other it would be kind of useless in terms of serving its purpose as a map then the Dymaxion like conformal from 1943 which attempts to transform the sphere into an icosahedron a shape with 20 sides then flattening out those 20 sides on a surface it preserves shapes and sizes very well but is heavily interrupted as a consequence but to be fair I think at this point the goal of the makers wasn't to create a useful map in the sense of it being good for navigating via sea land or air they were or are just trying to make the most accurate depiction of a globe on a flat surface and finally the share name one from 1982 which I just find extraordinary because it really takes the whole stretched Antartica thing to a max it depicts the world in a semicircle being centered on the top centre in the North Pole and having the southern pole stretched all around its limits so that is a quick overview of map projections why he exists why they are all necessarily inaccurate how some of them prioritize depicting some aspects correctly and others not depending on what they were made for and how some of them have attempted to be the most accurate possible there's literally hundreds of other projections that I couldn't fit them all into a video with an acceptable length so if you're interested in this just google it and you'll find endless 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 I will see you next time for more general knowledge

Channel: General Knowledge

Views: 51,709

Rating: 4.9426112 out of 5

Keywords: generalknowledge, funwithflags, countriesthatdon'texist

Id: NAzy4S4EOwc

Length: 13min 20sec (800 seconds)

Published: Fri May 29 2020

Reddit Comments

[u/lerobinbot]

nice