Wednesday, 25 April 2018

WALRUS: the Wirral and Liverpool Regional Urban System

On a recent trip to Liverpool I needed an all-day ticket that would let me use public transport across the city. So I bought a couple of day passes for me and a friend, which meant getting a plastic card that can be topped up, kind of like the Oyster Card in London. But in Liverpool it's called the Walrus card. It's not exactly the same as the Oyster, but it is named after a sea creature, though it took us a few moments to figure out why they chose Walrus as the name. But of course we decided it must really stand for Wirral and Liverpool Regional Urban System (surely, yes?) and I therefore had to make an animated gif of commute flows in the WALRUS, so here I am. Watch it multiple times to see the main travel to work patterns, and scroll to the bottom for a slower version. I've tried to get the colours right so you can see the mix of destinations clearly. Liverpool city centre is near the L of Liverpool and I've also labelled some other locations including the airport (Liverpool John Lennon Airport, as it is officially called).

Behold: commuter flows in the WALRUS

Surely the people who came up with Walrus really meant it as a play on the Beatles song plus a play on this urban and regional acronym. After all, there is a history of this kind of thing in the wider area, with SELNEC as 'South East Lancashire, North East Cheshire' probably the most famous example, from the late 1960s to the early 1970s. But no, if I Google it, I get absolutely nothing, as you can see below or try for yourself. Surely somebody already uses this, it seems too obvious. If not, then I will claim partial credit alongside my good friend for creating this backronym.

"WALRUS, you say?"

From the JR James Archive

There are other examples of urban and regional acronyms in the UK and across the world (feel free to suggest more) but I can't think of one that incorporates a nice local reference like this. Although, if they chose Oyster in London because it means the world is your Oyster then the Walrus thing doesn't work so well here ("The World is Your Walrus"!?). Anyway, it did make travel on public transport much more efficient and it also meant I got to revive my series of animated gifs, for an area I know pretty well.

My Walrus card

The other side of my Walrus card

That's really all there is to it for now. Hope to catch you next time I'm in the WALRUS, which really is a regional urban system. If you get the chance, I'd like to hear about other urban and regional acronyms you may have heard of. I'll end this post with another version of the gif at the top of the pages, this time slowed down a bit more.

The WALRUS in slow motion

Tuesday, 27 March 2018

Daytime Population Density

My last blog post on population density was basically just a little extract of some work I've been doing on population density. However, density is not absolute or fixed and it can change significantly throughout the day. A variety of sources suggest that the maximum density per square kilometre in the UK is around 25,000. Yet this only relates to where people live. Spend any time in a busy city centre and you'll see far higher densities than this, so I thought I'd take a look at it. To begin with, here's a map of daytime population density in the southern and eastern part of England.

The maximum density during the day is over 125,000 per sq km

As you can see on the map above, when we look at population density during the day, there are some big differences - the most obvious of which are in central London. Compare this to the picture when we look at residential population density, which is how it is usually reported.

This is also useful, but it's only part of the story

This is not particularly surprising, of course, but it is quite striking how large the differences are. Thanks to the folks at the Centre for Ecology & Hydrology, and an open licence, we can look more closely at daytime population density across the UK, as well as residential density, using 2011 data. This can provide us with a much more nuanced view of population density and help us understand how the population distribution changes during the working day. Outside London, the single square kilometre with the highest workday population is in central Glasgow, with over 60,000 people. A little extract of this, and the equivalent residential population is shown below.

Glasgow has the highest daytime population density in Scotland

Edinburgh has the highest residential density in Scotland

With this data we can then drill down to look at other parts of the UK, and this is what I've done in the rest of this post. I've extracted images for all areas where there are more than 20,000 people present in any single 1km cell during the working day, according to the CEH figures. As you'd expect, it includes the major cities but some of the places that do feature may surprise you and some of the places that don't may also. Only places with a single cell containing 20,000 people or more during the working day are shown.

You'll also notice the connection between density and rail infrastructure if you look closely. It often looks like a cable plugged into individual red squares. The upper figure in each image is the daytime population, with the residential figure in brackets underneath. Each cell is, of course, 1km by 1km. Click on the individual images to enlarge.











London - overview 
London - zoomed in

London - Tower Hamlets

London - maximum values







That's it for now. I'll return to look at population density in the future, hopefully once I've finished my current overly-ambitious attempt to derive some new-fangled population density measures for the whole of Europe.

Data source: this data is made available under the Open Government Licence. ©NERC (Centre for Ecology & Hydrology). Contains National Statistics data © Crown copyright and database right 2011. Contains data supplied by Natural Environment Research Council.

Reference: Reis, S.; Liska, T.; Steinle, S.; Carnell, E.; Leaver, D.; Roberts, E.; Vieno, M.; Beck, R.; Dragosits, U. (2017). UK Gridded Population 2011 based on Census 2011 and Land Cover Map 2015. NERC Environmental Information Data Centre.

Sunday, 28 January 2018

The Most Densely Populated Square Kilometre in 39 European Countries

A few days ago I published a short piece in The Conversation about population density across Europe, based on EU gridded population data. This was really my attempt to see if I could produce some numbers which better reflect the experience of population density across Europe, rather than just the raw arithmetic average. At the end of the piece I added a table with some stats, including the maximum 1km population density for each of the 39 countries I looked at. There wasn't space in the article to tell you where all these places were, so I'm doing it here instead. So, without further ado, here are the most densely populated 1km squares in each of the 39 countries, from Spain to Liechtenstein. Click to enlarge.

I did this quickly so it's a bit rough and ready as far as the maps go - a few labelling blips here and there but you can get the idea. Scrolling through from most dense to least dense does generally seem to make sense visually though you can't always tell what's what because some places have lots of high rises in them and you don't get a sense of that from the aerial photos.

Notes: the data are from 2011, so a little old now. We should also really consider these estimates, for a variety of reasons, but I think they are likely to be close to truth, based on my analysis of similar datasets (e.g. ONS in the UK and GHSL globally). Note that if you download the EU data you'll have to then join it to some kind of geodata (e.g. shapefile) because it's not already done. This can be tricky with about 2 million 1km cells and rows of data. Why are England, Northern Ireland, Scotland and Northern Ireland separate here? That's just the way they published the data. But I found it useful to get a better look at patterns in different parts of the UK.