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"On flat maps, it’s impossible to represent land mass size on a relative scale." Um, no it's not. TechCrunch needs better editors. You just need to use a non-M
by Bud 8y ago
"On flat maps, it’s impossible to represent land mass size on a relative scale."
Um, no it's not. TechCrunch needs better editors. You just need to use a non-Mercator projection.
https://en.wikipedia.org/wiki/Gall%E2%80%93Peters_projection https://en.wikipedia.org/wiki/Gall%E2%80%93Peters_projection
- astrodust 8y agoYou can represent size or shape correctly, not both. Anyone who uses the Gall-Peters projection is a cop.
- rm_-rf_slash 8y agoObligatory XKCD https://www.xkcd.com/977/ https://www.xkcd.com/977/
- hackme1234 8y agoYour username is obsolete in Ubuntu. It simply gives an error message.
- Ajedi32 8y agoGoogle decided to go with "A Globe".
- deathanatos 8y agoAt low zoom levels. Given the behavior of the poles (they're not viewable; the south is also a black hole…), I suspect that there's a very smoothly done transition to web mercator for the higher zoom levels.
- gefh 8y agoCorrect. At high zooms, the trig required in the spherical math becomes inaccurate, so we fade back to simple web mercator.
- astrodust 8y agoCartography wouldn't be able to use all these cheap tricks if the poles were habitable territory. Can you imagine the distortion on a map of a small town located at the pole if Mercator was used?
- sp332 8y agoYou can get pretty close though. Like a Dymaxion map (shown in sibling's XKCD link) or one of those orange-peel maps if you have enough little slices. Edit: better Dymaxion link https://en.wikipedia.org/wiki/Dymaxion_map https://en.wikipedia.org/wiki/Dymaxion_map It's made of triangles that you can rearrange, which isn't really shown in the xkcd.
- LeoPanthera 8y ago> You can represent size or shape correctly, not both. You can if you don't mind having a non-rectangular map border. https://en.wikipedia.org/wiki/Dymaxion_map https://en.wikipedia.org/wiki/Dymaxion_map
- polishTar 8y agoDymaxion maps are still deformed, just not as much as most other projections.
- jbob2000 8y agoThat's still not an accurate map. 3D maps don't have projection issues, they can have near perfect representation of the world.
- jacobolus 8y agoThe eyes see a 2-dimensional picture. Computer displays produce a 2-dimensional picture. There is no such thing as a “3D map” on a standard computer display. Only an orthographic (or maybe perspective) projection which animates in response to user input. In general an orthographic projection is a poor choice. The thing going for it is that it is easy to understand by analogy to a physical globe, and human spatial understanding can partially compensate for the distortion by imagining a sphere. But there are also disadvantages, for example on an orthographic projection north is not always vertical, latitude and longitude lines are neither perpendicular nor straight, shapes and areas can be very dramatically distorted near the edge of the map, there are dramatic distance errors between far away points or points not in the center of view, it is impossible to view more than half of the planet’s surface in one view, etc. There are many other choices of map projections, and for any particular purpose, some other projection is usually better.
- mikeash 8y agoRegardless of what the eye sees, the brain perceives three dimensions. This projection happens to be the one that the brain can automatically unpack into an accurate 3D representation. Technically, things near the edges are squished and distorted, but that gets undone in the wetware.
- jacobolus 8y agoYou really can’t get an accurate sense of angles/shapes, areas, distances, or directions with an orthographic projection except by moving the view around. Even when you do, it is very difficult to accurately compare attributes of regions which are far away on the globe, and easy to mislead yourself. (This is a problem with physical globes as well.) For many types of mapping use cases, orthographic projections are substantially worse than other possible choices. Sometimes physical spheres (or virtual representations of spheres as dynamic orthographic or perspective projections) are nice. That’s why I spent a whole bunch of time building myself a spherical chalkboard, for example. But they aren’t the best choice for any purpose. Personally I don’t think they make a very good choice for a general-purpose world map. They are better as a supplement to flat maps.
- nikofeyn 8y agoit's a theorem of differential geometry that we cannot have a (perfectly) accurate 2d map of the earth.
- mrb 8y agoThe author of TFA didn't write "perfectly accurate" but "land mass size on a relative scale". Bud is correct.
- nikofeyn 8y agothe author of TFA probably thought the desire for correct shape in a map is implied and wasn’t trying to defend against map pedantry. of what use is a map if the shapes are wrong?
- kccqzy 8y agoOne of the revolutions in the first Underground/Subway/Metro maps was that by throwing away the actual shapes, it is able to represent the stations and the relationships between them far clearer than otherwise.
- nikofeyn 8y agoa subway map has little to do with a geographic map. only the nodes and time traveled between them matter. the shape of the actual routes is immaterial.
- hackme1234 8y agoFrom the first line of the article. The Gall–Peters projection is a rectangular map projection that maps all areas such that they have the correct sizes relative to each other. Like any equal-area projection, it achieves this goal by distorting most shapes.
- rorosaurus 8y agoIt's much cheaper to make an incorrect statement and let people correct you for free, then edit the article! ;)