Shooter localization in wireless sensor networks

Shooter localization is considered in a wireless network of microphones. Both the acoustic muzzle blast (MB) from the gunfire and the ballistic shock wave (SW) from the bullet can be detected by the microphones and are considered as measurements. The MB measurements give rise to a standard sensor network problem, similar to time difference of arrivals in cellular phone networks, and the localization accuracy is good provided that the sensors are well synchronized compared to the MB detection accuracy. The detection times of the SW depend on both shooter position and aiming angle, and we demonstrate that estimation based on these measurements can potentially also reveal the shooting direction beside the position, but again this requires good synchronization. We propose to base the estimation on the time difference of MB and SW at each sensor, which becomes insensitive to synchronization. Cramer-Rao lower bound analysis indicates how a lower bound of the root mean square error depends on the synchronization error for MB and MB-SW differences, respectively. Results from field trials with different type of ammunition show excellent accuracy of the proposed method for both the position and the aiming angle of the shooter.