China is using mobile phone signals to map its ghost cities

Some of the ghost cities identified by Baidu researchers. Image: Baidu.

You'd think it'd be relatively hard to mislay a city. Cities are, by definition, very large things: losing one sounds like it should be much more challenging than losing, say, your car keys, or even your entire car. 

But in China, there are entire cities which go relatively unaccounted for. This is the result of a combination of fast development, low regulation, and the fact that many Chinese cities are still practically empty. 

This is why it's pretty hard to get a figure for just how many "ghost cities" – cities that exist, but lack residents – there are in China. Most of these cities have some residents, making "ghost" a relative, and pretty hard to define, term. 

So Baidu (basically, China's Google) decided to work it out. The researchers behind a new study, "Ghost Cities: Analysis Based on Positioning Data in China", used location data from users' phones, plus mapping and building location data, to find areas with high volume of buildings, but a low density of people. The researchers also tried to discount vacant areas that were empty because of tourism: apartments only filled in high tourism season, for example. 

Here are some areas of vacant housing they found in nine different cities: 

Overall, the researchers say they found over 50 ghost cities, though they only revealed around 20 in the report, so as not to adversely effect the real estate market in the rest. (No comment.) 


As the researchers admit in their conclusion, this isn't a conclusive study: it relies, first and foremost, on the idea that "Baidu users" are a good proxy for "people", and that areas with no Baidu activity are empty. Yet as they note, arrogantly and probably accurately:

With the ubiquity of smart mobile phones, Baidu users occupy the most proportion of the whole population. 

This does seem to be one of the more accurate surveys of China's ghost cities produced so far, even if the researchers won't release all the details. That could mean greater accountability for the development firms who toss up concrete blocks and then fail to fill them. 

 
 
 
 

Meet the Museum of London's latest exhibit: a disgusting, giant lump of fat

A pipe clogged with lovely, lovely fat. Image: Thames Water.

The Museum of London has been teaching visitors about the capital’s history for over 50 years now. It contains exhibits on the Romans, the Plague, the Great Fire and the Blitz. It even houses the Lord Mayor’s Coach, a great red and gold thing, which horses pull about the streets of the City each November for the Lord Mayor’s Show.

So it’s presumably in keeping with this tradition, of presenting the most educational and most beautiful artefacts from London’s history, that the museum’s newest exhibit will be a congealed mass of fat, oil, grease, wet wipes and sanitary products.

The Lord Mayor’s Coach and the fatberg (left). Image: Tony Hisgett/Wikimedia Commons (coach); Museum of London (fatberg).

The “monster fatberg”, a press release informs me, is “London’s newest celebrity, and has fascinated and disgusted people all over the world”. Found in the sewers beneath Whitechapel, the entire ‘berg was over 250m long (6m longer than Tower Bridge!) and weighed in at 130 tonnes.

The Museum won’t house the entire fatberg, alas. Most of it, the press release tells me, has been converted into biodiesel, “turning a nauseating waste problem into a cleaner-burning, greenhouse gas reducing fuel which will benefit the environment”. One relatively small chunk, though, has been donated to the Museum by Thames Water to promote its “Bin it – don’t block it” campaign, which encourages Londoners to, well, you can work that part out for yourself.


So what, I hear you wondering, is a fatberg, exactly? Where do baby fatbergs come from?

Well, as the name suggests they’re the result of cooking fat, poured down sinks to congeal in sewers. Assorted wipes and napkins are also involved, playing roughly the same role that fibre does in your gut. I wouldn’t think about it too much if I were you.

In 2014, back in the early days of CityMetric when fatbergs were all the rage, we learned that there are even fatberg groupies, including a couple who had visited one in situ in the sewers as an anniversary trip. Righto.

We wouldn’t recommend that, to be honest, but if you fancy seeing a chunk of one from within the safety of the Museum of London, it’ll be on display from 2018. Knock yourselves out.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason. 

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