Mollweide v. Hammer (map projections)

Please compose all posts in Emacs.

Moderators: phlip, Moderators General, Prelates

User avatar
Qaanol
The Cheshirest Catamount
Posts: 3035
Joined: Sat May 09, 2009 11:55 pm UTC

Mollweide v. Hammer (map projections)

Postby Qaanol » Tue Sep 02, 2014 2:28 am UTC

I don’t think I’ve ever started one of these before but…what the heck, let’s do this thing.

Image
Mollweide
is an equal-area map projection in a 2:1 ellipse. Lines of latitude are horizontal though not equally spaced, while meridians are ellipses.

Image
Hammer
is an equal-area map projection in a 2:1 ellipse. It has lower distortion than Mollweide, especially toward the edges.

I say Hammer is superior. Just look at Antarctica, or at the lines of latitude converging on the north pole. Seriously, what is Mollweide doing there? The meridians all come into the pole horizontally—it doesn’t even make sense! Hammer, on the other hand, gives a nice visual impression of a world that was cleanly unwrapped from a globe, and conveys all the appropriate sense of curvature.
wee free kings

User avatar
Flumble
Yes Man
Posts: 1944
Joined: Sun Aug 05, 2012 9:35 pm UTC

Re: Mollweide v. Hammer (map projections)

Postby Flumble » Tue Sep 02, 2014 11:41 am UTC

Back in the day map projections used to be relevant, but we have globes, 3D rendering and GPS nowadays. Don't even mention demographic charts, because they're skewed anyway (unless it's a professional map with properly inserted proper research data, but how often do you see those anymore?) and misused in buzzfeeds.

Still, if I have to choose, the CS guy in me says Mollweide. It's got parallel lines. :D
If only Hammer would've been a conformal map, then it would get my vote.

EvanED
Posts: 4324
Joined: Mon Aug 07, 2006 6:28 am UTC
Location: Madison, WI
Contact:

Re: Mollweide v. Hammer (map projections)

Postby EvanED » Tue Sep 02, 2014 1:59 pm UTC

3D rendering of those is the only one I buy. Globes have been around as long as reasonably accurate maps (ones where worrying about the projection is worthwhile). For things you get out of a GPS (navigation) you should probably just pick Mercator and be done (or perhaps the Gnomic projection, which maps great circles to straight lines, if you're in a boat or plane), so if you believe the fancier equal-area projections were revant, GPS doesn't affect that either.

User avatar
EvilDuckie
Posts: 386
Joined: Sun Nov 02, 2008 4:29 pm UTC
Location: The Netherlands

Re: Mollweide v. Hammer (map projections)

Postby EvilDuckie » Wed Sep 03, 2014 6:04 am UTC

Funny enough I consider Mollweide to be preferable over Hammer, for general mapping purposes. Its distortions seem to be less. So if I were to make a general map of the world, and the size in the layout would work out I'd pick Mollweide over Hammer.

Map projections each have their pros and cons and despite what Flumble says they're still pretty darn relevant. A large part of the mapping nowadays is still intended for flat surfaces, be it a piece of paper or a screen (or, in a recent project I did, a slab of stone measuring 16 x 12 feet). Or... to make maps for a globe you often still need to go through a 2D medium before it gets on to the 3D globe, and that's again where you need to worry about projection.
Quack!

User avatar
Qaanol
The Cheshirest Catamount
Posts: 3035
Joined: Sat May 09, 2009 11:55 pm UTC

Re: Mollweide v. Hammer (map projections)

Postby Qaanol » Thu Sep 04, 2014 3:45 am UTC

Flumble wrote:Still, if I have to choose, the CS guy in me says Mollweide. It's got parallel lines. :D
If only Hammer would've been a conformal map, then it would get my vote.


Hey now, those parallel lines are purely an artifact of the specific orientation of the map. For instance, if we move to 60ºN, 30ºW, with the top of the map pointing east, and then rotate 90º at the end, we get…

/me codes up some FreeMat scripts right quick

…this:

Image Image

Mollweide on the left, Hammer on the right. See? Parallel lines are gone!

Although…the part where the equator hits the edge looks much better in Mollweide, for exactly the reasons that I didn’t like its meridians at the poles earlier. Mollweide is also better at Antarctica and Australia now too. Gah!

…at least Hammer has the latitudes much more circular near the north pole?
wee free kings

Derek
Posts: 2149
Joined: Wed Aug 18, 2010 4:15 am UTC

Re: Mollweide v. Hammer (map projections)

Postby Derek » Sat Sep 06, 2014 6:57 pm UTC

EvanED wrote:For things you get out of a GPS (navigation) you should probably just pick Mercator and be done (or perhaps the Gnomic projection, which maps great circles to straight lines, if you're in a boat or plane), so if you believe the fancier equal-area projections were revant, GPS doesn't affect that either.

Mercator here has the advantage that since it doesn't distort shapes, the map can essentially be saved as a large flat image, and any particular local region can be displayed without distortions by zooming in on the image. Other projections requires you to recalculate the projection when you move the center of the map to avoid distortions. This is why most online maps (Google Maps, Bing, Mapquest), which are primarily intended for looking up local areas, use Mercator. The new Google maps still uses Mercator for the map mode, but uses a 3D globe for satellite view (though I suspect it switches to Mercator when you zoom in).

User avatar
EvilDuckie
Posts: 386
Joined: Sun Nov 02, 2008 4:29 pm UTC
Location: The Netherlands

Re: Mollweide v. Hammer (map projections)

Postby EvilDuckie » Mon Sep 08, 2014 6:08 am UTC

Actually, Mercator doesn't distort small shapes, which is why it's good for local use. Larger shapes are distorted up to the point where it's mathematically impossible to display the north and south pole on a Mercator projection.
Quack!

Derek
Posts: 2149
Joined: Wed Aug 18, 2010 4:15 am UTC

Re: Mollweide v. Hammer (map projections)

Postby Derek » Mon Sep 08, 2014 1:05 pm UTC

It doesn't distort angles, would be the proper (mathematically correct) way to say what I meant. But the point is that you can get a good map of any local area without re-projecting the map.

User avatar
Qaanol
The Cheshirest Catamount
Posts: 3035
Joined: Sat May 09, 2009 11:55 pm UTC

Re: Mollweide v. Hammer (map projections)

Postby Qaanol » Thu Apr 07, 2016 11:33 pm UTC

Well, a year and a half later I’ve changed my mind—I like Mollweide better now.

And I just dusted off my old scripts to generate Mollweide maps at lots of different perspectives, then manually combed through hundreds thousands of results to find the good ones. Here are five of the best:

Tilt-back (aka. “Normal-looking map”)
Image
Center: (15°S, 11°E), Rotation: 0°

Antarctica (aka. “The great southern ocean”)
Image
Center: (75°S, 60°E), Rotation: 90°

Atlantic ocean (aka. “Sideways”)
Image
Center: (60°N, 0°E), Rotation: 75°

Indian ocean (aka. “Paired continents”)
Image
Center: (45°N, 45°E), Rotation: 135°

Pacific ocean (aka. “Ring of fire”)
Image
Center: (30°N, 180°E), Rotation: 135°

The last two could be rotated 180° to put Antarctica in the bottom half of the map, but this is how they came out of my code (which stops before 180° rotation to avoid duplicates). Also, I like the Pacific map much better this way—it really draws attention to the expanse of water.

The “tilt-back” projection is very similar to a “standard” map, but centered slightly south of the equator so Antarctica is all in one piece. My code actually produced a nearby map which split Alaska across the edge, and I manually ran nearby longitudes until I hit on 11°E which makes the edge cut through Bering strait.
wee free kings

User avatar
somitomi
Posts: 444
Joined: Fri Nov 06, 2015 11:21 pm UTC
Location: can be found in Hungary
Contact:

Re: Mollweide v. Hammer (map projections)

Postby somitomi » Sun Jan 15, 2017 8:05 pm UTC

Image

But I like these rotated maps, there's something about them being kind of familiar but strange at the same time.
Image
they/them/theirs = he/him/his ❖ If you want to use something else out of dadaist spite, I won't mind.
✆ Hello? This is Forum Games Discord, what is your emergency?

User avatar
pogrmman
Posts: 326
Joined: Wed Jun 29, 2016 10:53 pm UTC
Location: Probably outside

Re: Mollweide v. Hammer (map projections)

Postby pogrmman » Sun Jan 15, 2017 11:23 pm UTC

EvilDuckie wrote:Funny enough I consider Mollweide to be preferable over Hammer, for general mapping purposes. Its distortions seem to be less. So if I were to make a general map of the world, and the size in the layout would work out I'd pick Mollweide over Hammer.



I'm the same. IMO Mollewide looks better for general global maps. I don't have particularly strong opinions on maps though.

User avatar
Qaanol
The Cheshirest Catamount
Posts: 3035
Joined: Sat May 09, 2009 11:55 pm UTC

Re: Mollweide v. Hammer (map projections)

Postby Qaanol » Sun Feb 05, 2017 9:14 pm UTC

somitomi wrote:I like these rotated maps, there's something about them being kind of familiar but strange at the same time.


Thanks, glad you like them! Here are a few more I found in my stash:

Diagonal 1 (aka. “Split Central America”)
Image
Center: (0°N, 75°E), Rotation: 60°

Diagonal 2 (aka. “Split Indonesia”)
Image
Center: (15°N, 75°W), Rotation: 45°

Diagonal 3 (aka. “New Zealand alone”)
Image
Center: (30°N, 18°W), Rotation: 30°

Sideways (aka. “Northwest passage”)
Image
Center: (60°N, 120°E), Rotation: 120°
wee free kings

User avatar
somitomi
Posts: 444
Joined: Fri Nov 06, 2015 11:21 pm UTC
Location: can be found in Hungary
Contact:

Re: Mollweide v. Hammer (map projections)

Postby somitomi » Sun Feb 05, 2017 9:44 pm UTC

Image
I'm now considering making a large print of several of these for my wall.
Image
they/them/theirs = he/him/his ❖ If you want to use something else out of dadaist spite, I won't mind.
✆ Hello? This is Forum Games Discord, what is your emergency?

User avatar
Qaanol
The Cheshirest Catamount
Posts: 3035
Joined: Sat May 09, 2009 11:55 pm UTC

Re: Mollweide v. Hammer (map projections)

Postby Qaanol » Sat Feb 11, 2017 2:42 am UTC

somitomi wrote:I'm now considering making a large print of several of these for my wall.

I can make them higher-res if you want.
wee free kings


Return to “Religious Wars”

Who is online

Users browsing this forum: No registered users and 5 guests