Wednesday 26 December 2018

One degree of population

Here I am at the end of the year with another bit of map fun, this time inspired by Bill Rankin's world population histograms from 2008 (check out his website if you haven't already - it's amazing). For no good reason, other than curiosity, I decided to do some mapping of the world's population by single degrees of latitude and longitude. Actually, curiosity is I think quite a good reason, so see the first graphic below, making sure to read the caution on the map (tl:dr not all cells are the same size). Update 28 December 2018 - I added a version doing it by longitude as well. There's a gif at the bottom of the page and the mp4 files are in the repo I link to below. I also did a backwards-forwards looping gif - see below.

I think this backwards and forwards version works well

It makes more sense to compare areas at the same latitude

In the image above, I've picked out the ten most highly populated 1 degree cells but of course they are not all the same size - they get smaller the further away from the equator you are, because the lines of longitude narrow towards the poles. But even so, I think it's probably safe to say the cell where New Delhi is has a lot of people in it, as do the other nine featured above.

Now, we all know that most of the world's population live in the northern hemisphere (I make it about 87%), which is hardly a surprise because that's where most of the land is (68%) but I thought it would be interesting to do an animation of the above map, and that's exactly what I did. Here are some stills from the animation (below) and here is a direct link to the repository where I've put a 15, 30 and a 60 second animation. You'll probably have to download the files before viewing them.

Before that, I've embedded a version from YouTube, with an audio track.

If you live below 30 degrees south you are quite special

People seem to like living where the land is

Above 30 degrees north is where it's at 
I'm one of the 5% - are you?

And by longitude? I did that too and those files are at the GitHub repo link above but here's a fast gif of it for now.

How I did this
The data I used for this is the GHSL world population dataset that I've written about before. I've been using it recently in a paper so thought I'd do something a little different with it. This is the latest data, for 2014. I used the 1km gridded population dataset and re-aggregated it by lat/long so it's not a precise match with lines of latitude and longitude but it's close enough to be a reasonable estimate. I mapped it in QGIS and exported a few thousand frames in QGIS Atlas then patched the video together using FFmpeg.