Here is a map showing the area covered by water for US Census Tracts. Each dot represents the surface area of 20 Olympic-sized swimming pools (because I, like most people probably, suck at visualizing/comprehending big square meter numbers).
Here is a simple how-to, including a poignant letter penned to my old friend, Dot Density.
Happy Dot Mapping! John
P.S. Wondering what the same map would look like but showing the area of land instead of the area of water? My equal-area projection ensures it’s a rather boring, but nerd-interesting, map:
Adventures In Mapping 
Cool stuff. Love how Missippi + Tributaries show up so well.
On another note, why do we always tend to use Olympic Swimming Pools as an area/volumetric measure? Does anyone outside the 0.01% of people who are avid indoor swimmers/Phelps fans know how big an Olympic size pool is, other than it’s big?
Football (american) fields seem like the best measure for me. Most people know seem to know it, and it’s standardised. Not saying that’s a better alternative, or I have an answer (flooded football fields was the best I came up with which seems much worse). Just something I think is worth talking about, to me it seems like one of those random norms that we keep on perpetuating out of habit, at least in my opinion.
There was a neat proportion test around recently with Web Mercator on Twitter involving countries relative size. I’d love to see that with Olympic Sized swimming pools vs other things (school buses parked end to end), football fields, tennis courts, etc
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Thanks! Yeah, that’s what caught my eye first, as well.
It’s funny you say that, the map was originally rendered in units of football fields! I drew the legend and everything. But then I thought about swimming pools and it fit so much better with the theme that I went for it (knowing that our sense of a pool’s area isn’t as strong as a football field’s).
On the other hand, if I had gone ahead with football fields most non-Americans would have a vague sense of that as well. Yards? The pointy sort of football? Oh well.
At the end of the day, both maps looked essentially identical, and it’s only practical as a curious look at the varied distribution of water bodies.
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Ha, that’s too funny, and good point. It would be a neat graphic to see Globally what different folks use as size comparisons for this rough scale of mapping.
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