Choosing color palettes for choropleth maps

Choropleth maps, the ones where regions are filled with colors based on data, grow easier to make. However, choosing colors, the number of colors, and the breakpoints is often less straightforward, because the answer is always context-specific. Lisa Charlotte Rost, now at Datawrapper, provides a rundown of the decision process.

The explanation is in the context of the Datawrapper tool, but you can easily apply the logic to your own workflow.

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Adjusting map data with Mapshaper

mapshaper-demo

Map making is a finicky challenge where oftentimes your map data — points, lines, and polygons — must align just right with your external data that exists as a CSV file or related. Mapshaper is an online tool that helps you massage your geographic data to where it needs to be.

The online application has been around for a while, but I only recently used it, and it’s kind of magical. It’s one of those things where you half expect the whole thing to fail, and then when it seems to be working you still expect there to be some wrinkle that makes using the tool a pain. Not so with Mapshaper.

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Nuclear detonations from 1945 to present

There have been over 2,000 nuclear detonations since 1945. Orbital Mechanics mapped each documented test in animated form. It's mostly about mood and the individual explosions. More journal-like, although not much annotation unfortunately.

Red represents atmospheric explosions, yellow represents underground, and blue represents underwater.

See also artist Isao Hashimoto's rendition from a few years ago. It's the same data with an entirely different feel.

[via kottke]

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Disappearing Arctic reflected in National Geographic maps

Shrinking Arctic

In the most recent update to their atlas coming in September, National Geographic explains the shrinking Arctic through the lens of previous atlas maps. It's not looking good.

As the ocean heats up due to global warming, Arctic sea ice has been locked in a downward spiral. Since the late 1970s, the ice has retreated by 12 percent per decade, worsening after 2007, according to NASA. May 2014 represented the third lowest extent of sea ice during that month in the satellite record, according to the National Snow and Ice Data Center (NSIDC).

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Possible float routes for Malaysia Airlines Flight 370

Possible float paths

Malaysia Airlines Flight 370 went down a year ago, and with recently found debris that is possibly from the flight, researchers have a few more bits of data to work from. The New York Times picked up on coverage of what's going on, and in the latest, they provide an animated map that shows possible routes the debris could have taken. This is based on computer models from the Commonwealth Scientific and Industrial Research Organisation, and suggests a search area.

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Exploding nation of poverty

Nation of Poverty

Poverty is on the rise. Justin Palmer mapped it for major cities in the United States.

Concentrated poverty in the neighborhoods of the nation's largest urban cores has exploded since the 1970s. The number of high poverty neighborhoods has tripled and the number of poor people in those neighborhoods has doubled according to a report released by City Observatory.

Instead of going with a choropleth map and filled polygons, Palmer went with sloped lines to show the change between 1970 and 2010. Longer lines mean greater absolute value, where red lines pointing up represent increased poverty and green lines pointed down represent decreased poverty.

I like it.

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United States electricity map

Power capacity

The Washington Post mapped power plants in the United States by type and capacity in megawatts. Color indicates the former, and bubble size indicates the latter. There are a lot more natural gas power plants, supplying 30 percent of the nation's energy, than I expected.

See the article for a map for each type, along with a state-level breakdown.

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Million dollar blocks and the cost of incarceration

Million dollar blocks

Incarceration costs a lot of money. We know this, sort of. But how much really? Million Dollar Blocks, by Daniel Cooper and Ryan Lugalia-Hollon, estimates the cost in Chicago, down to the block level.

The map is based on data obtained by the Chicago Justice Project from the Cook County Circuit Court. It represents all adult convictions between the years of 2005-2009. For each conviction, we have data for what the offense was, the length of the sentence, and the offender's residential address.

We derive dollar amounts from sentence lengths. Our cost assumption is that, on average, the Illinois Department of Corrections spends approximately $22,000 per year for each inmate. Life sentences are calculated based on average life expectancy.

As you might expect, a bulk of arrests occur in concentrated areas, hence the name of the project. Darker red means higher estimated costs.

Spending numbers appear in the bottom right corner when you mouse over blocks, but the map could use a legend to get a better sense of scale. It'd be especially helpful when you switch between all offenses and just drug-related ones. When you switch from the latter (the default view), which is a subset of the former, over to all offenses, the map becomes less red. But the spending is actually more.

Anyways, I hope they work on this more. It's a good concept, and naturally, I'm wondering what it's like in other places.

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Map of literary road trips

Literature road trip

Ever wanted to follow in the footsteps of a famous writer or literary character in their journey across the country? Well now you can. Richard Kreitner for Atlas Obscura hand-cataloged the road trips — more than 1,500 entries — from twelve works of literature and Steven Melendez mapped the paths.

The above map is the result of a painstaking and admittedly quixotic effort to catalog the country as it has been described in the American road-tripping literature. It includes every place-name reference in 12 books about cross-country travel, from Mark Twain's Roughing It (1872) to Cheryl Strayed's Wild (2012), and maps the authors' routes on top of one another. You can track an individual writer’s descriptions of the landscape as they traveled across it, or you can zoom in to see how different authors have written about the same place at different times.

Pair this with the BreweryMap, which tells you nearby breweries during a road trip, and you've got yourself an adventure.

Happy travels.

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Hand-drawn map boundaries

Hand-drawn boundaries

You've probably seen those "maps" where people from other countries draw the United States and end up with a wobbly New York, Los Angeles, and some stuff in the middle. Here's what happens when cartographers draw boundaries by hand. It's called Project Linework.

[T]he power of cartography (and its purpose) is that it’s not realistic. It’s highly abstracted and generalized, and reality went out the window once we decided to show a road as being red and give it a stroke width that makes it look hundreds of miles wide, or to replace a city with a black circle. We stylize so many other things on maps, but playing around with the actual shapes of states, islands, or roads, is uncommon. I’d like that to change. I want to shake things up, because I think that people become too familiar with the shapes of states and countries and the like. They’re default, unobtrusive. It's hard to call attention to places when they always look the same.

Download the hand-drawn boundaries, in styles such as Elmer Casual and Wargames, in various formats to suit your needs. [via National Geographic]

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