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"Yet when you look objectively at the impact a map projection has on the beliefs and world view of the general populace, you really don’t come up with much. Map

"Yet when you look objectively at the impact a map projection has on the beliefs and world view of the general populace, you really don’t come up with much. Maps are only a tiny part of most people’s lives. They’re exposed to many projections anyway—as they should be. They take cues from a map in many ways, not just relative sizes. And mostly, they really don’t care." Well, personally, I've never been exposed to other projections until 28 years of age and that was only because I happened upon an article about how wrong mercator projection is on Hacker News. While it really is a tiny part of my life and I don't really care, the realization that Africa is huge and almost three times bigger then Europe and that Greenland is tiny is something I consider an important thing to know - and probably changes some of my views on things (for instance I never quite understood how Africa has so many countries - which if you triple it's size, it becomes much clearer).

daanstrebe 11y ago
"Well, personally, I've never been exposed to other projections until 28 years…" That is vanishingly unlikely. These are projections you have practically certainly seen: https://www.mapthematics.com/ProjectionsList.php?Projection=84#Robinson https://www.mapthematics.com/ProjectionsList.php?Projection=... https://www.mapthematics.com/ProjectionsList.php?Projection=189#Winkel%20tripel https://www.mapthematics.com/ProjectionsList.php?Projection=... https://www.mapthematics.com/ProjectionsList.php?Projection=69#Mollweide https://www.mapthematics.com/ProjectionsList.php?Projection=... https://www.mapthematics.com/ProjectionsList.php?Projection=159#orthographic https://www.mapthematics.com/ProjectionsList.php?Projection=... And many others. Also, people often mistake any rectangular projection for Mercator. I have even seen this happen in academic literature.
kuya 11y ago
conformality and area are preserved on globes, both physical and virtual (like in google earth). as a kid, i remember thinking africa was huge from the globes that teachers had in classrooms. in ~2007 or so, i actually tried to buy a physical globe for my desk. i went into a couple office supply stores and the high school age employees had never even heard of a globe. it was the strangest thing trying to explain what a globe was: "it's like a ball with a map on it".
alexqgb 11y ago
The thing is, all projections are wrong in some sense. That's an unavoidable fact when transposing between flat surfaces where the angles in triangles always add up to 180 degrees, and triangles on curved surfaces where they don't. For instance, on a flat plane, given a straight line with two lines perpendicular (i.e. both at 90 degrees), those two lines will be parallel, and will not form a triangle with the base. But on a globe, two lines of longitude that are both at 90 degrees to the equatorial line will nevertheless converge at the pole. Depending on how far apart they are, the sum of the angles in a triangle on a curved surface can approach 360 degrees. What this means is that it's mathematically impossible to express triangles that work on a curved surface using triangles that work on a flat plane, because the latter is limited in ways that the former is not. In other words, in going from curved figures to flat ones, you're going to have to distort something. Your three choices are shape, distance, and direction. The more a projection preserves one, the more it's going to have to distort another. Some projections try to strike a balance, others focus on one aspect at the expense of another. The Mercator - which was originally designed for mariners - opted to preserve direction, and did so at the expense of shape, and, to a lesser degree, distance. So instead of a map where the distance between degrees varies at different points on the map, Mercator provides uniform measures of degree at every point. That means you can pick a location on the map, draw a straight line to your desired destination, note the angle formed by that line and magnetic and / or polar north, then set a course along that bearing with full confidence that you'll arrive where you want to. As far as direction goes, Mercator is absolutely correct. To visualize how this works, see this Wikipedia article showing Tissot's Indicatrix on a sphere, then see this Esri writeup and note that on a Mercator, all the indices are perfect circles. http://en.wikipedia.org/wiki/Tissot%27s_indicatrix http://en.wikipedia.org/wiki/Tissot%27s_indicatrix http://blogs.esri.com/esri/arcgis/2011/03/24/tissot-s-indicatrix-helps-illustrate-map-projection-distortion/ http://blogs.esri.com/esri/arcgis/2011/03/24/tissot-s-indica...

daanstrebe 11y ago

"Well, personally, I've never been exposed to other projections until 28 years…" That is vanishingly unlikely. These are projections you have practically certainly seen: https://www.mapthematics.com/ProjectionsList.php?Projection=84#Robinson https://www.mapthematics.com/ProjectionsList.php?Projection=... https://www.mapthematics.com/ProjectionsList.php?Projection=189#Winkel%20tripel https://www.mapthematics.com/ProjectionsList.php?Projection=... https://www.mapthematics.com/ProjectionsList.php?Projection=69#Mollweide https://www.mapthematics.com/ProjectionsList.php?Projection=... https://www.mapthematics.com/ProjectionsList.php?Projection=159#orthographic https://www.mapthematics.com/ProjectionsList.php?Projection=... And many others. Also, people often mistake any rectangular projection for Mercator. I have even seen this happen in academic literature.

kuya 11y ago

conformality and area are preserved on globes, both physical and virtual (like in google earth). as a kid, i remember thinking africa was huge from the globes that teachers had in classrooms. in ~2007 or so, i actually tried to buy a physical globe for my desk. i went into a couple office supply stores and the high school age employees had never even heard of a globe. it was the strangest thing trying to explain what a globe was: "it's like a ball with a map on it".

alexqgb 11y ago

The thing is, all projections are wrong in some sense. That's an unavoidable fact when transposing between flat surfaces where the angles in triangles always add up to 180 degrees, and triangles on curved surfaces where they don't. For instance, on a flat plane, given a straight line with two lines perpendicular (i.e. both at 90 degrees), those two lines will be parallel, and will not form a triangle with the base. But on a globe, two lines of longitude that are both at 90 degrees to the equatorial line will nevertheless converge at the pole. Depending on how far apart they are, the sum of the angles in a triangle on a curved surface can approach 360 degrees. What this means is that it's mathematically impossible to express triangles that work on a curved surface using triangles that work on a flat plane, because the latter is limited in ways that the former is not. In other words, in going from curved figures to flat ones, you're going to have to distort something. Your three choices are shape, distance, and direction. The more a projection preserves one, the more it's going to have to distort another. Some projections try to strike a balance, others focus on one aspect at the expense of another. The Mercator - which was originally designed for mariners - opted to preserve direction, and did so at the expense of shape, and, to a lesser degree, distance. So instead of a map where the distance between degrees varies at different points on the map, Mercator provides uniform measures of degree at every point. That means you can pick a location on the map, draw a straight line to your desired destination, note the angle formed by that line and magnetic and / or polar north, then set a course along that bearing with full confidence that you'll arrive where you want to. As far as direction goes, Mercator is absolutely correct. To visualize how this works, see this Wikipedia article showing Tissot's Indicatrix on a sphere, then see this Esri writeup and note that on a Mercator, all the indices are perfect circles. http://en.wikipedia.org/wiki/Tissot%27s_indicatrix http://en.wikipedia.org/wiki/Tissot%27s_indicatrix http://blogs.esri.com/esri/arcgis/2011/03/24/tissot-s-indicatrix-helps-illustrate-map-projection-distortion/ http://blogs.esri.com/esri/arcgis/2011/03/24/tissot-s-indica...