Sg2009wc:shots

From She's Geeky Wiki

Title: Spotshotter Gunshot Location

Session: 7-C Bay Area Jan 2009

Conveners: by El White and Sarah Newman

Note-taker:' Alison Chaiken

Attendees:

• Deborah Smead
• Elenor Reffel
• Madelene Kahn
• Lucy Li
• Judith Bush
• Kathy Lass
• Dee Elling
• Rupa Eichenberger
• Stephanie Bergman

Notes:

SpotShotter (SS) is deployed in about 30 cities dating back to 2003. The system helps cities get police officers to where shooters are both on a long-term statistical basis and as part of incident response. The core technology is a time-of-flight system based on3 different kinds of acoustic detectors: simple microphones, small acoustic arrays ("azimuth detectors") and a few more sophisticated detectors. The system presents a police dispatcher with a map or overhead imagery with shooter location predicted as a red dot.

Analysis of captured audio is done on a per-incident basis at the nodes using the Audacity package. Nodes communicate to a relay station via WiFi on longer term deployments. The relay station has wireline ethernet and communicates to a central server. FOr short-term deployments (VIP events, freeway shooters, etc.), nodes with cellular modems are used.

Two sensors locate a shooter on a hyperbola. Three give an estimated fix, while more will give a more reliable solution.

Time- and frequency-domain analysis helps to differentiate noises from gunshots, which have a distinctive pattern. Metadata (time of day, day of year, other noises like laughter or alarms) are also presented to dispatchers. The classifiers are also trained using a Bayesian algorithm based on years of accumulated incident reports. The fact that gunshots are louder than most background noise is very helpful.

Time-syncing of sensors is accomplished via GPS since time-of-arrival analysis depends on exact synchronization.

SpotShotter is a profitable and expanding business located in Mountain View, CA. The military buys systems in addition to police departments.