Gall-Peters: I hate you

May 12, 2021 1:18 PM

xkcd's "Map Projections", animated [via mefi projects]
posted by biogeo (39 comments total)

And then you realize that even the "globe" is being projected on a flat video screen. Whoa!
posted by SPrintF at 1:40 PM on May 12, 2021 [3 favorites]

Why, I am looking at my hand right now. Why do you ask?
posted by chavenet at 1:48 PM on May 12, 2021 [2 favorites]

ce c'est ne pas une globe
posted by subtle_squid at 2:05 PM on May 12, 2021 [3 favorites]

And even 3D globes are projected onto your flat retinas! Woah.
posted by biogeo at 2:10 PM on May 12, 2021 [2 favorites]

My retinae are not flat, they're shaped like the insides of spheres! (approximately)
posted by aubilenon at 2:19 PM on May 12, 2021 [3 favorites]

Your retina is a sphere. With the right equipment, you could project a geometrically accurate map onto the back of your eyeball.
posted by Hatashran at 2:19 PM on May 12, 2021 [6 favorites]

I much prefer the 1:1 scale raised relief map I'm standing on right now. It takes a while to get the big picture, and I get lost occasionally, but it's fun and I (think I ) have time.
posted by OHenryPacey at 2:21 PM on May 12, 2021 [26 favorites]

I much prefer the 1:1 scale raised relief map I'm standing on right now.

Atmospheric distortions blur detail, and I could do without the effects of the gravity well.
posted by justsomebodythatyouusedtoknow at 2:26 PM on May 12, 2021 [4 favorites]

I keep confusing all these projections with the territory.
posted by Richard Saunders at 2:26 PM on May 12, 2021 [12 favorites]

I like the Dymaxion map, and I look at a lot of things thru 3D goggles. I do not, however, own shoes with toes. Gotta draw the line somewhere.
posted by Artifice_Eternity at 2:27 PM on May 12, 2021 [5 favorites]

Oooh, I was just discussing map projections with my kids (7 and 11). I think the thing that they enjoyed most was the site which allows you to drag outlines of countries over a map using the Mercator projection.

This Vox video was also great.
posted by Quack at 2:30 PM on May 12, 2021 [7 favorites]

Good point about the retina being spherical! Arguably, the fact that most of our perceptual sensitivity is concentrated at the fovea makes the perceptual space flatter, but then that's like combining the problem of map projections with cartograms.

... Has anyone ever made a cartogram on the surface of a globe? I want to see one now.
posted by biogeo at 2:43 PM on May 12, 2021

What your favorite ragtime music says about you.
posted by 3.2.3 at 2:45 PM on May 12, 2021 [2 favorites]

Worked at a map store in college. Loved it.
posted by TigerMoth at 3:07 PM on May 12, 2021 [2 favorites]

Alternate Mercator: you really like tiled, zoomable web maps.

Mollweide: you're actually an astronomer.

If you like looking at projections the D3 docs have a nice collection in schematic form. Also this comparison document lets you look at various projections scored on some significant criteria.
posted by Nelson at 3:29 PM on May 12, 2021 [1 favorite]

biogeo: "And even 3D globes are projected onto your flat retinas! Woah."

And the images on the retinas are mapped onto a directed small-world network in our brains. Woah!
posted by signal at 3:56 PM on May 12, 2021 [2 favorites]

The activity states of which are now frequently represented by researchers as several-dimensional manifolds with complicated curvature fields, embedded within much higher-dimensional spaces, visualized in two dimensions using a variety of projective geometry tricks not fundamentally dissimilar to those used to map the surface of a sphere onto a two-dimensional plane! Wo-ho-ho-hoa!
posted by biogeo at 4:42 PM on May 12, 2021 [2 favorites]

Oh my gosh that is the best thing on the web!
posted by brambleboy at 4:52 PM on May 12, 2021 [2 favorites]

I like maps with sea monsters and dragons drawn on the parts we haven't been to yet...
posted by WalkerWestridge at 5:01 PM on May 12, 2021 [6 favorites]

Spilhaus: You're a sea monster.
posted by Makwa at 5:13 PM on May 12, 2021

Mollweide: you're actually an astronomer.

What, I haven't even commented in this thread yet!
posted by mollweide at 5:27 PM on May 12, 2021 [10 favorites]

We're all living in our own personal azimuthal equidistant projections anyway
posted by scruss at 5:27 PM on May 12, 2021 [2 favorites]

Gee, none of the projections/descriptions fit me at all... oh shit I'm on the wrong planet
posted by Greg_Ace at 6:28 PM on May 12, 2021 [4 favorites]

The only map projection I've ever actually made was a map of the moon. See, I'd stuck some sensors in a lunar globe to report the latitude and longitude of a moveable reticle, and wanted a Max patch to look up what feature (mostly craters and maria) it was pointing at.

The real point is what map projection is best depends entirely on what you need it for, and for this weirdo application equirectangular was without a doubt the correct choice. Mercator gets a lot of hate, but for stuff like navigation software, it's not bad - if you want a conformal projection where north is always up, are there even other options?
posted by aubilenon at 6:31 PM on May 12, 2021 [1 favorite]

Came for the Waterman, was not disappointed.
posted by oddman at 7:22 PM on May 12, 2021 [1 favorite]

> We're all living in our own personal azimuthal equidistant projections anyway

Spoken like a true topologist!
posted by scose at 8:12 PM on May 12, 2021

Claim: nobody under 25 cares about world maps or their projections.

I'm over 25, I own zero 3D goggles, and I gotta say this is unfair to the Dymaxion, to rotate land masses across its triangle boundaries. Animate the triangles flipping around to optimize land contiguity!
posted by away for regrooving at 8:17 PM on May 12, 2021 [3 favorites]

In my heart, I know the Peirce quincuncial projection is the one found in the Great Ocean on the Ringworld.
posted by straight at 11:51 PM on May 12, 2021 [2 favorites]

Can someone explain what is happening in the animations?
posted by starfishprime at 3:49 AM on May 13, 2021

I do have a framed Waterman Projection on my wall. And I’m free for dinner, if someone can babysit the kids.
posted by triage_lazarus at 5:07 AM on May 13, 2021 [1 favorite]

I have to admit that I don't know anything about maps but I do own several pairs of shoes with toes. So now I know that I must like the dymaxion map without doing any research on maps. Hooray!
posted by ensign_ricky at 5:32 AM on May 13, 2021 [1 favorite]

Hatashran: Your retina is a sphere. With the right equipment, you could project a geometrically accurate map onto the back of your eyeball.

Soooooooo... which projection would best do that?

What's the Retinal Projection?
posted by clawsoon at 6:58 AM on May 13, 2021

starfishprime: Can someone explain what is happening in the animations?

I'll try. Every map is a projection from a globe onto a flat sheet. These animations are what happens if you spin and then roll the globe that's "behind" the projection.

I feel like it could be explained better. Hmm...
posted by clawsoon at 7:02 AM on May 13, 2021 [2 favorites]

That's a good explanation, clawsoon! My view on it is that the animations are moving the center of the map. Most map projections are designed so that 0 latitude, the equator, is at the middle of the projected map (the flat image you're looking at). That seems very natural; it is the middle of the earth physically. Some maps also "center" at 0 longitude, through Greenwich Observatory (more or less). That's not really "natural", there's no physical law that says that's the middle of the earth east to west. But it's a common convention. Most map projections work fine no matter what longitude you pick as "center" (although not the sliced up ones). But few work well if you move the center latitude.

What the animations are doing is they're moving that center point on the projected map from 0, 0 on the globe to other spots. Movement of the longitude coordinate generally doesn't make map projections look weird. But moving the equator often looks really weird. In particular it's great for calling out all the geometric distortions inherit in most map projections. Flat maps tend to hide the ugliest deformations at the poles, since folks mostly don't care what those look like on a map. (The basic Google Mercator projection used in web maps literally cannot show the poles!) If you re-center the projection so that 35N is at the very top of the projected map suddenly the United States looks very strange in almost all map projections.

Another tool useful for understanding projection distortions: Tissot's Indicatrice. Basically you draw a true circle on the earth's surface, then look at the distorted oval you get in most projections.
posted by Nelson at 8:13 AM on May 13, 2021 [2 favorites]

I'd just add one thing to that great explanation. By moving the center of projection around in an amination, it gives you an immediate qualitative sense of the distortions of that projection. The Dymaxion has very little!
posted by Carmody'sPrize at 9:57 AM on May 13, 2021

Dymaxion may have very little distortion, but it's pretty useless for finding what's near where. The few newer printed atlases have subtle distortion contours around each page, telling you that stuff outside the contour is outside useful accuracy.

Also, for good but brain-hurty stuff about projections: USGS Map projections: A working manual.
posted by scruss at 10:49 AM on May 13, 2021

I much prefer the 1:1 scale raised relief map I'm standing on right now.

Obligatory
posted by gimonca at 12:55 PM on May 13, 2021 [1 favorite]

Thanks, people!
posted by starfishprime at 1:10 PM on May 13, 2021 [1 favorite]

I just spent way too much time am just getting started on the Wikipedia List of map projections page.
posted by indexy at 1:16 PM on May 13, 2021