
Rotate the World - jgrahamc
http://richarddmorey.org/map/
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nthitz
Jason Davies' also did this with many more projections than mercator. Fun to
browse
[https://www.jasondavies.com/maps/transition/](https://www.jasondavies.com/maps/transition/)

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amelius
Fun indeed.

It would be nice to know the advantages of each of these projections, and why
they were developed.

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jacobolus
Start with
[http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.ht...](http://www.progonos.com/furuti/MapProj/Normal/TOC/cartTOC.html)

If you want formulas,
[https://pubs.er.usgs.gov/publication/pp1395](https://pubs.er.usgs.gov/publication/pp1395)

If you want to know more, there are many books about cartography.

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mikeash
Are we ever going to be able to get rid of Mercator, or are we doomed to
having people think that Greenland is as big as Africa until the end of time?

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rspeer
You shouldn't want to actually "get rid" of Mercator entirely. Mercator is
pretty great for interactive maps on the Web. Conformal angles, north is
always up, splits nicely into tiles.

As long as Africa and Greenland aren't on the same map, it's got almost
everything that you want from a map.

Of course, what's best for an interactive map is if it turns into a globe when
you zoom out, like Google Earth. instead of being a shitty global Mercator.
That's a lot more graphically complex, though.

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robbrown451
Why not have it stay as a globe when you are zoomed in? It will be similar to
Mercator, but the aspect ratio would be more accurate especially as you get
further from the equator.

Admittedly, it is easier for developers who are adding features if you do it
as Mercator, but not that much easier (if it has a good API).

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rspeer
I don't know what you mean about the aspect ratio further from the equator.
Mercator is conformal, it preserves angles, so the aspect ratio is 1:1
everywhere that it makes sense to say "aspect ratio".

Are you talking about the problem with the shape of a Mercator tile becoming
absurd very close to the poles, which I wouldn't call "aspect"? Or are you
thinking of the equirectangular projection, where the aspect ratio changes to
preserve the distance between latitude lines?

The reason not to use a globe is efficiency. Not only is 2D easier than 3D,
but you can make Mercator out of tesselated tiles. You can't do that on a
globe without having way too many tiles or obvious seams.

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robbrown451
Right but things like google maps doesn't really use tiles anymore as far as I
can tell, they do it using vectors. Tiles suck for lots of things, for
instance scrolling can move the street name off the visible map, while doing
it as vectors the name can be adjusted.

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rspeer
The tiles aren't static raster images, but they're still tiles, made of vector
data. You can see them while it's loading. This allows Google to cache the
files they serve.

And when you pan a Google Map, you're panning a flat Web Mercator projection.
If it were a projection of the globe, then everything that's already been
rendered would have to be adjusted by imperceptible subpixels to account for
the curvature of the Earth.

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robbrown451
Well if it vector data, the "tiles" can simply be a region of a sphere. That
alone is not a reason for Mercator.

There may be efficiencies of panning a flat projection, but that is becoming a
smaller and smaller issue as devices get more capable.

Also, even when in "map mode", you will often notice that google maps is doing
more than that. Go to a place where there are tall buildings (I'm looking at
downtown san francisco) and you can see the perspective shift on the buildings
as it pans.

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mrgriscom
Also this: [http://mrgris.com/projects/merc-
extreme/](http://mrgris.com/projects/merc-extreme/)

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jacobolus
For more along these lines,
[http://archive.bridgesmathart.org/2013/bridges2013-217.pdf](http://archive.bridgesmathart.org/2013/bridges2013-217.pdf)

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pcunite
When I was a kid, getting access to maps and globes was like a revelation. Now
look at us, spinning something the size of the earth in web page. If you like
looking at things from this orientation, give the celestiaproject.net a try.

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gedy
This is wonderful, some of the first programming I did was to try and do this
in GWBASIC on a 286 many years ago. It's magical to see this in realtime in
your browser.

