https://xkcd.com/977/
Yeah, Randall is great and this was a fun comic, even though it skips some of my favorite projections and makes some dubious other choices. Some comments (about the comic and the projections shown):
- I’m surprised there was no mention of paired stereographic projections of hemispheres, considering that was the most popular way to present the globe for at least a couple hundred years (e.g. the one I showed upthread) and considering how important the stereographic projection is in complex analysis, and as a basis for constructing other conformal maps. Or at least he could have included some other projection with paired hemispheres in circles. I kinda like this one from 1825 (
source):
- It’s interesting that the Mercator projection is presented in a square, the way you might see it on Google Maps. Historically it has almost never been presented in a square.
- The Van Der Grinten projection is somewhat obscure nowadays, isn’t all that close to a Mercator projection, and in its most popular incarnation wasn’t presented inside a circle (below left). For a globe-in-a-circle projection which obviously parallels the mercator projection, why not show the Lagrange projection (actually first presented by Lambert) instead (below right)? (Actually I can answer that myself: this whole comic is heavily biased towards projections used by National Geographic for making whole-world maps.)
- Goode’s projection was sorta neat in the 20s when it was introduced, but really shouldn’t be used today. It’s perfectly fine that it’s included in this comic, as its the best known example of an interrupted projection, but wow is it an ugly stitch job. The seam between the sinusoidal and elliptical (Mollweide) portions is a glaring flaw, even if you decide you want the interruptions as Goode chose them. Speaking of sinusoidal and elliptical equal-area projections, those surely deserve a spot for their historical importance and continuing use today. e.g. these three elliptical maps used for showing the cosmic microwave background radiation, the oceans, and a fun “Atlantis” transverse version:
- I don’t think the Hobo–Dyer projection deserves a place there as separate from Gall’s version. There’s nothing much to distinguish it from every other aspect ratio of the
equal-area cylindrical projection.
Fun Fact: The State Plane Coordinate System is based upon either a Lambert Conic Conformal Projection or the Transverse Mercator Projection generally depending on whether the state primarily runs N to S or W to E. The U.S. as a whole is projected with Universal Transverse Mercator.
Yep, conformal projections are especially nice if you can restrict yourself to a small area or trace along a line.
The UTM system is kind of interesting, it cuts the globe up into a whole bunch of skinny north-south strips. Unfortunately these can’t quite overlap perfectly, so when you need to move from one zone to another it’s a bit of a pain in the ass. It definitely makes sense if you’re a big organization who needs to operate worldwide but demand high precision in locating things to use a relatively orderly system like UTM though and a world-relevant datum like WGS 84. See also
https://en.wikipedia.org/wiki/Military_grid_reference_systemLambert conformal conic projections are great for mapping anything that runs roughly along a parallel. Some choice of standard/transverse/oblique Mercator, stereographic, or Lambert conformal conic projections is almost always a fairly reasonable choice for a projection, and they’re all well understood and easy to communicate about.
Source: Geomatics student
What does a Geomatics student study? Any interesting projects?
