Monday, 3 October 2011

Comparing Populations: Night Time vs. Day Time

Esteemed Canadian and fellow researcher Brian Webb, from the University of Manchester, recently sent me an interesting image which compares the population of Washington D.C. in the day to the population at night. This got me thinking. I did a bit of digging and found some of my old data. Put simply, I had two datasets for wards in the North West of England. One file contained the resident population of wards and the other had the population of wards during the day time (i.e. residents, minus out-commuters, plus in commuters). Out of this came two visualisations, as shown below (red peaks = more people) and a short video.

I also decided to turn this into a very simple animation, which is embedded below. I have also produced a larger version of this on its own page. Note: the video embedded below will keep playing once you click play. The larger version allows you to pause the video and watch at your own pace.

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Although these are really just some pretty pictures there are some important points to be made here. We think about the population of places - and the associated local costs and constraints - in relation to resident population but in some areas the day time population is so high that the impact on the local area is far out of proportion to the size of the resident population. Another matter is the well known issue of spatial mismatch or, more generally, understanding the differences between where people live and where people work and the implications of this. 

In short, understanding the spatiality of populations is important for planning and policy purposes - these visuals are just a simple way of telling the story of data. This is important because the data on display here comes from an analysis of a commuting data matrix of 1000 x 1000, or one million cells of data. So, another point here is that data on its own is not information, as we all know.