Carlo Ratti points to an undulating line on a graph on his computer that shows wireless Internet usage at MIT over time. “The heartbeat of MIT,” he says. In October, the MIT campus became home to one of the largest Wi-Fi networks in the country, with 2,800 access points providing wireless Internet service in all academic and residential buildings. Ratti, a practicing architect who also runs the SENSEable City Laboratory in the Department of Urban Studies and Planning, wants to study how people work in and move through physical spaces on campus. So he maps real-time usage of MIT’s Wi-Fi hubs in a project he calls iSpots.

“Because of wireless and because of laptops, people now work in a different way. There is much more flexi­bility,” says Ratti. “Somebody might be in the bar or in the lounge working.” Today, almost all MIT students own laptops, which have liberated many faculty and researchers from their desks as well. By giving architects and urban planners information about where and how newly untethered Wi-Fi users can do their work, Ratti hopes to help them design better buildings and better cities.

[For images of Wi-Fi activity in and around the MIT campus, click here.]

Every 15 minutes, Ratti’s lab collects data from Information Services and Technology log files that track how many people are connected to 2,600 of MIT’s 2,800 wireless access points. (For wireless users who agree to be identified, the log files also record who they are.) That data is converted into real-time maps and statistics posted at ispots.mit.edu.

The heartbeat graph shows that on weekdays, Wi-Fi usage peaks during business hours, sharply declines as staff go home, holds steady until midnight, while students work in the dorms, then bottoms out at 6:00 a.m. “Friday evening, activity starts to drift away….Sunday, people start thinking about Monday, and they panic, so they work again,” says Ratti. The graph can be refined to show wireless usage by campus area, building, floor, or room.

People can elect to be tracked on an iSpots website diagram that maps their locations to as close as five meters. “You can make decisions about where you go and what you do based on where other people go and what they do,” says Ratti. “You might be able to schedule a meeting in a dynamic way” by locating people and picking a central location.

“In the past, [planners] have relied on interviews or observations interpreted by mathematical models” to understand how people use the built environment, says Dennis Frenchman, professor of urban studies and planning. “With better information, we can test options more easily and design better, more functional places. At another level, sensing patterns of use will facilitate the design of spaces that respond in real time, adapting themselves hourly or daily to new demands or desires.” Rooms, for example, might change color and lighting depending on who is inside. Traffic lights could be programmed so that their timing changes according to the locations of commuters’ cell phones. In fact, Ratti’s lab has tracked cell-phone movement in two European cities to test the feasibility of just such a system.

The ability to pinpoint people’s locations using their Wi-Fi connections or cell phones could prove critical after a natural disaster. But it also raises major privacy concerns – and questions about who owns location data. Ratti says that big corporations want to retain control of the data they collect. Google, he says, is “giving a free Wi-Fi infrastructure to San Francisco, but they want to be able to develop business models based on how people use it.” Ratti wants to develop novel location-based applications but believes that people should control their own location data. After all, sometimes you just want to be off the grid.