Traditional city maps visualize just one aspect of urban design--the city’s intended structure, full stop. But add in a layer that visualizes how people actually use the city, and then the map becomes much more interesting. Eric Fischer did exactly that when he used Twitter’s API to collect tens of thousands of geotagged tweets and map them onto the streets of New York, Chicago, and the San Francisco Bay area. The maps amount to something close to a desire path on a macro scale: The maps show where our buses and subways should be, if they conformed to the way we actually move and live.
They are essentially inkblot visualizations of where the density of urban flow is highest. (Thicker black lines mean more people passing down that road, street, or mass transit line.) The statistical and mathematical methods used to generate the maps will be of interest to cartographic data nerds (I’m looking at you, Tim De Chant), but laypeople can appreciate the patterns that emerge. In one visualization of the Bay Area, Fischer notes that "Telegraph is the street most neglected by existing rapid transit infrastructure."
Fischer’s maps are yet another example of the kind of powerful information that networked, ubiquitous sensors can provide. The MTA in New York City is spending billions of dollars to expand its mass transit system; how might a map like Fischer’s inform decisions on where, when, and how to dig new subway lines? With regard to the Bay Area, Fischer notes that "BART does not do a very good job of serving the most promising corridor in Berkeley and North Oakland. … Needless to say, if this were to be constructed, it would have to be pretty much entirely in subway to avoid tearing down the neighborhoods it would intend to serve."
Commenters on Flickr are already beseeching Fischer to offer his maps as large format art prints. In the meantime, you can peruse the details of his maps in our slideshow.