Seoul, South Korea, spent millions of dollars embedding sensors in its main arteries in an attempt to capture real-time traffic data. It didn’t work. The information was never accurate. But in 2012, the city installed a wireless payment system that uses GPS technology in 25,000 taxicabs. The information from the GPS sensors gave the city the real-time traffic information it always wanted, but at a fraction of the cost of embedding sensors in the road.

Installed sensors have been around for a while, but now cities are turning to mobile sensors to help capture valuable data to monitor traffic and the environment. For example, Chicago put GPS devices on every city-owned vehicle, turning them into instant traffic monitoring stations.

But what about turning citizens into sensors? In Santander, Spain, anyone can download a city-built app to their smartphone and use it to find out what’s happening at venues they happen to be passing by. But the app also lets citizens upload information of their own, geocode it and send it to the city, so that others can share the information. The idea is to allow citizens to send as well as receive information that can become part of the overall data set. “It’s kind of like a tech version of community watch,” said Katharine Frase, chief technology officer of IBM Public Sector.

The more that people are involved with sensor-based projects, the better a city can understand the reality of what’s going on, in terms of what people really want rather than what city government thinks its citizens want. “It’s a way to capture the pulse of the city,” said Carlo Ratti, director of MIT’s SENSEable City Lab.

One recent project under way in Copenhagen involves turning bicycles into sensors. “We are turning them into mobile sensing units,” Ratti said. “It allows you to collect data about your cycling activity and about your surroundings, creating a big pool of data that everyone can share from.”

Some have cautioned against expecting too much from citizen-based sensor projects. But Ratti is confident that they will play an important role in the future of cities. “I believe that people will be the key actors in sensing, five to 10 years from now,” he said. “The next stage will be based on bottoms-up sharing of data instead of top-down sensing as it’s now done in many cities.”

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Tod Newcombe  |  Senior Editor

With more than 20 years of experience covering state and local government, Tod previously was the editor of Public CIO, e.Republic’s award-winning publication for information technology executives in the public sector. He is now a senior editor for Government Technology and a columnist at Governing magazine.