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April 25, 2007

Wired 15.04: Shot Spotter

From Wired 15.04: Shot Spotter:

A great article on the shot spotter technology (gunshot detection system). It covers how the system works, the history of the technology, and how it is currently being deployed. Its a nice long article with lots of detail. Here are some snippets:

In October, the department spent $350,000 to install 84 ShotSpotter sensors on rooftops, utility poles, and other inconspicuous places over 6 square miles of urban blight. Since then, dispatchers have received roughly a dozen automatic alerts every day, each one an opportunity to get officers to the scene of a shooting while the gun is still smoking. [Oakland, CA]

"In the past, the best information the police could hope for was a neighbor calling to say, ‘Sorry to bother you, but there may have been a shooting somewhere in my neighborhood,'" says ShotSpotter CEO James Beldock. "Our system can immediately tell them that, say, 11 rounds were fired from a car going 9 miles an hour, northbound, in front of a specific address on Main Street. In some situations, ShotSpotter could get someone on the scene within a minute. That's a level of situational knowledge police have never had."

This kind of coverage requires an array of 12 to 20 specialized sensors per square mile. Roughly the size of a medium pizza and designed to look like a rooftop fan, each sensor contains up to four small microphones. If one of these units detects a loud noise, it forwards a recording to a server at police headquarters along with three pieces of information: location, time, and general direction the sound came from. If a sound is detected by only one sensor, it's probably too quiet to be gunfire, and in any case, the system needs data from three sensors to pinpoint the location of a noise. If several sensors report an event at the same time, the server gets to work. First, the software performs an analysis to categorize the noise as gunfire, firecrackers, bottle rockets, helicopters, or other. If it determines the event was a gunshot, the program makes a simple calculation to triangulate the sound's origin to within 80 feet or less.

The upgrade caught on fast. Chicago, Gary, and Washington, DC, bought systems in 2005 and 2006. . . . Meanwhile, ShotSpotter expanded from the mean streets of the US to the blast zones in Iraq. In 2006, the Army deployed a specialized battlefield version. The user interface is mobile, and so are the sensors themselves; soldiers carry units roughly the size of a Tom Clancy paperback. The sensors pinpoint enemy fire while a camera on an unmanned Boeing scan Eagle aircraft overhead targets the threat.

The improved sensor arrays deployed in US cities show even more promising results. Two days after Rochester, New York, activated 6 square miles in July 2006, local police arrived on the scene of a shooting in time to make an arrest. Since then, the array has been solely responsible for roughly one gun-related arrest per month.

The 2-square-mile grid in Gary recorded 10 to 15 incidents a day when it was installed in 2005. Police used the system to confiscate 45 illegal weapons on New Year's Eve of that year, and shooters began to think twice. Now the system picks up one or two hits a day.

Posted by rshah at April 25, 2007 11:27 AM

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