Gunfire locator

These systems are used by law enforcement, security, military, government offices, schools and businesses to identify the source and, in some cases, the direction of gunfire and/or the type of weapon fired.

The DGA & Section Technique de l’Armée de Terre (STAT), the French Army’s engineering section subsequently commissioned Metravib D. to find a solution for shot detection, a way to assist soldiers and peacekeepers who come under fire from snipers without knowing precisely where the shots were coming from.

In late 1992, John C. Lahr, a PhD seismologist at the nearby United States Geological Survey, approached the Menlo Park police department to ask if they would be interested in applying seismological techniques to locate gunshots.

Lahr modified the software typically used for locating earthquakes and recorded the data at a higher sample rate than is used for regional seismology.

After gunshots were heard, Lahr would determine their location while his wife monitored the police radio for independent confirmation of their source.

Indirect flashes that bounce off nearby structures such as walls, trees, and rocks assist in exposing concealed or limited line-of-sight detections between the weapon and the sensor.

The combination of a muzzle blast and a shockwave provides additional information that can be used along with the physics of acoustics and sound propagation to determine the range of a discharge to the sensor, especially if the round or type of projectile is known.

Assault rifles are more commonly used in battle scenarios where it is important for potential targets to be immediately alerted to the position of enemy fire.

Infrared detection systems have a similar advantage at night because the sensor does not have to contend with any solar contributions to the background signal.

Due to their ability to sense at great distances, to sense in a non line-of-sight manner, and the relatively low bandwidth required for transmitting sensor telemetry data, systems deployed for law enforcement, public safety and homeland security in the United States have primarily been based on acoustic techniques.

[5] Another method of classifying gunfire uses "temporal pattern recognition," as referred by its developer, that employs artificial neural networks that are trained and then listen for a sound signature in acoustic events.

Information in the network is coded in terms of variation in the sequence of all-or-none (spike) events, or temporal patterns, transmitted between artificial "neurons".

These neural networks can then be trained as "recognizers" of a target sound, like a gunshot, even in the presence of high noise[citation needed].

Optical discriminating had previously consisted of methods, among them spatial, spectral, and creative temporal filters, to eliminate solar glint as a false alarm.

Earlier sensors could not operate at speeds fast enough to allow for the incorporation of matched temporal filters that now eliminate solar glint as a false alarm contributor.

Most stand-alone systems have been designed for military use where the goal is immediately alerting human targets so they may take evasive and/or neutralization action.

Military systems generally rely on both the muzzle blast and projectile shockwave "snap" sounds to validate their classification of gunfire and to calculate the range to the origin.

Distributed sensor arrays have a distinct advantage over stand-alone systems in that they can successfully classify gunfire with and without hearing a projectile "snap" sound, even amid heavy background noise and echoes.

In addition to urban cityscapes, the distributed-array approach is intended for area protection applications, such as critical infrastructure, transportation hubs, and campuses.

Using common data-networking methods, alerts of the discharges can be conveyed to dispatch centers, commanders, and field-based personnel, allowing them to make an immediate assessment of severity and initiate appropriate and decisive force response.

Similarly for the protection of critical infrastructure, where the information is clearly and unambiguously conveyed in real-time to regional crisis command and control centers, enabling security personnel to cut through often inaccurate and delayed reports so they may react immediately to thwart attacks and minimize subsequent activity.

In public safety and law enforcement, gunshot location systems are often used in high-crime areas for rapid alerts and awareness into the communications and dispatch center where the alerts are used to direct first responders to the scene of the gunfire, thus increasing arrest rates, improving officer safety, securing witnesses and evidence, and enhancing investigations, as well as in the long run deterring gun crimes, shootings and especially "celebratory gunfire" (the practice of shooting weapons in the air for fun).

Gunshot location systems based upon wide-area acoustic surveillance coupled with persistent incident data storage transcends dispatch-only uses because reporting of urban gunfire (via calls to 9-1-1) can be as low as 25%,[6] which means that law enforcement agencies and their crime analysts have incomplete data regarding true activity levels and patterns.

[citation needed] Additional benefits include aiding investigators to find more forensic evidence to solve crimes and provide to prosecutors to strengthen court cases resulting in a higher conviction rate.

With the accuracy of a gunshot location system and the ability to geo-reference to a specific street address, versus a dearth of information that typically is the case when citizens report gunfire incidents to 9-1-1, agencies can also infer shooters by comparing with known criminal locations, including those on parole and probation; investigators can also at times infer intended victims and hence predict and prevent reprisals.

[7] As of 2016, detection systems were deployed to a number of cities, including Baltimore, Maryland Bellwood, Illinois; Birmingham, Alabama; Boston; Canton, Ohio[citation needed]; Cambridge, Massachusetts; Chicago; Hartford;[8] Kansas City; Los Angeles; Milwaukee; Minneapolis; New Bedford, Massachusetts; Oakland; Omaha; San Francisco; Springfield, Massachusetts;[9] Washington, D.C.; Wilmington, North Carolina;[10] New York City;[11] Integration with cameras that point in the direction of gunfire when detected is also implemented.

[12] San Antonio, Texas discontinued its $500,000 ShotSpotter service, after finding it had only resulted in four arrests[13] and seven weapons confiscated in the 15 months it has been in operation.