The contours of Twitter

Strange Maps is a fascinating blog of, well, unusual maps, generally accompanied by interesting analysis of what they might tell us about ourselves. The example that led me to the site was a map of Twitter traffic in London.

I'm a bit surprised that more than one commenter is skeptical of the data on the grounds that financial centers like the City show less traffic than areas like Soho. Wikipedia describes Soho as "predominantly a fashionable district of upmarket restaurants and media offices" (which sounds about right) while the City I recall (from a decade or so back) rolled up the sidewalks around dusk as the white-collar crowd headed out to go homeward or pubward to relax.

Hmm ... is one more likely to tweet from the offices of some bank or trading house with the boss nearby, or while relaxing at an "upscale restaurant" afterwards -- or for that matter working at a "media office" during the day? Likewise for the case of Wall Street vs. New York's SoHo and La Defense vs. Levallois in Paris, particularly as Levallois is (Wikipedia again) "one of the most densely populated municipalities in Europe".

I'm more curious what the map would look like normalized for population, that is, tweets per person in a given area as opposed to raw tweets. Are there more tweets in central London than in the surrounding suburbs because there are more people? Also interesting would be a breakdown of both raw and normalized volume by time of day. The raw volume would at least to some degree track the flow of people in and out of the city, while the normalized volume would be affected both by that and by people's daily habits.

[Happily, Strange Maps is still in business, and still keepin' it strange --D.H. Dec 2015]

The new NASA/METI map

NASA and Japan's Ministry of Economy, Trade and Industry (METI) have just released the most complete topographic map of Earth, ever. The dataset covers 99% of the Earth's surface, from 83 degrees north to 83 degrees south, with elevation measured every 30 meters. Put this together with a good GPS and adequate storage, and you've got a never-lost device that would have seemed like sheer magic during most of recorded history.  Or so one might think.

In purely technical terms, cartography and navigation have seen revolutionary changes in the past few decades. In practical terms, the picture is a bit less clear. Most of us spend most of our time in a few, fairly small, well-known areas, a fact which leads to some interesting implications on privacy. Outside that comfort zone, a GPS can certainly be useful in finding one's way through unfamiliar streets, but a printed map will do in a pinch, or in cases of absolute desperate need, stopping somewhere and asking directions.

Similarly, commercial shipping and aviation follow well-known routes and for decades have had specialized equipment for staying on course. It's not clear what difference a better map of the Earth's surface would make.  In the air and at sea it's more important to know where you are than what's below you, except when you're landing or putting in to port.  Unless it's a dire emergency, you'll be doing that in a well-known place, and if it is a dire emergency, the new map is probably the last thing on your mind.

Radio navigation is about a century old. Satellite navigation works better and has been taking over, particularly on the seas. I'm not an expert on shipping and transport, but I have no doubt it has opened up and will continue to open up new possibilities.  In the air, the FAA and its sibling agencies are working to enable point-to-point "air taxi" services which forgo the established flight corridors and fly directly between small airports. (This has been in the works for years, though. The hurdles are not only technical, but legal and economic).  In either case, technology is making a difference, but the real difference is in navigation, not mapping.

So ... the new map database is definitely cool, and making it freely available to the world is even cooler. If I'm planning an expedition to Patagonia or the Yukon, I'll definitely want to consult it. For my morning commute, not so much.

[Rereading, it seems to me that elevation every 30 meters is only of so much use without some indication of roads, place names and so forth, and 30 meters is plenty of room to hide all sorts of hazards.  As wonderful a research tool as I'm sure the map is, it's probably adds little or no value over previous maps when considered as a navigation aid.   The NASA/METI press release in the news tends to confirm this: the gaps filled in were mainly in "very steep terrains and in some deserts", as one might expect --D.H. May 2015

This is the rare article that I've edited more than lightly on re-reading.  The original version shifted abruptly to radio and satellite navigation without really saying why.  I've tried to make that clearer.  I may not have reconstructed the original argument, but I think the current version at least makes some coherent argument --D.H. Jan 2016]