ShotSpotter is the audio-sensing technology that alerts police in D.C. and about 90 other cities to when and where a gun has been fired by measuring the distance from its many sound sensors. Within 45 seconds, it can provide not only a detailed location for the origin of the gunfire, but also the actual sounds for an officer to listen to as they speed to the call.
In terms of advanced technologies aimed specifically at firearm related crime, Three Technologies are using for that :-
- ShotSpotter™– A real-time gunshot detection and location system.
- GunOps™– GunOps is a firearm-crime investigative tool used by police to help map firearm crime, search for trends and evidence, and hunt for suspects.
- IBIS – (Integrated Ballistic Identification System), an integrated technology solution consisting of hardware and software which enables the sharing and comparison of significant quantities of exhibit information and images across a network of imaging sites, as well as the automated identification of likely matching bullets or cartridge cases.
How does ShotSpotter works?
A system recently deployed in Washington, D.C., called ShotSpotter, relies on an acoustics-based, GPS-equipped system that automatically locates the origin of the shot and notifies authorities. A series of acoustic sensors picks up the sound waves of a muzzle blast that radiate outward from the barrel in all directions.
The heart of the system is acoustic triangulation. While the exact technical details of the ShotSpotter system are proprietary, we can get a fairly good idea of how the system works by looking at the process of triangulation.
ShotSpotter uses 10 to 12 sensors spaced evenly throughout each square-mile section of the city it’s covering, and each sensor is capable of hearing the sound of gunfire within a 2-mile (3-km) radius.
Because the speed of sound is a known entity — 340.29 meters per second (0.21 miles per second) at sea level — the difference in the time it takes for the sound of a gunshot to reach three different sensors can determine the location of that gunshot. Using a built-in GPS system as an accurate time source, three sensors work together to triangulate the location from which a shot was fired. Here’s an overview of how a system like this might work:
- A shot is fired somewhere in the city. Sensor 1 picks up the sound of the shot. Since each acoustic sensor has a range of about 2 miles, all we know right now is that the shot was fired within a 2-mile radius of Sensor 1.
- One second later, a second sensor picks up the sound waves of a gunshot. If sound in this city travels at about 0.21 miles per second, we now know that the shot was fired approximately one-fifth of a mile farther away from Sensor 2 than from Sensor 1. We can draw a circle representing the perception radius of Sensor 2 overlapping the perception radius of Sensor 1 — since both sensors picked up the sound waves, the shot must have been fired within the overlapping coverage areas. Where the two circles intersect, we have two possible locations for our gunshot.
- To figure out which of these two points is the location from which the shot was fired, we need to find a third sensor that picked up the sound of the shot. A third sensor, located to the south of Sensors 1 and 2, picked up the sound waves a half-second after Sensor 2 detected them. This would put the origin of the sound about one-tenth of a mile farther from Sensor 3 than from Sensor 2.
We now have our gunshot location, at least in terms of distance from the sensors. The system then uses built-in GPS receivers to convert that known point into latitude and longitude coordinates, and passes the information to the nearest system base station via either phone lines (for wired sensors) or radio-frequency signals (for wireless sensors). The base station forwards the coordinates to the nearest 911 call center, which has the equipment to convert those coordinates into addresses and cross streets. The 911 call takers dispatch police to that location. According to ShotSpotter, the system is accurate to 25 meters (82 feet) or less — far less than the length of a typical city block.
The sensors themselves are about the size of a thick stick of gum. Each one is enclosed in a weatherproof box about half the size of a loaf of bread, which is typically situated on a rooftop or telephone pole. According to ShotSpotter, the sensors are sensitive enough to tell the difference between a gun shot and a car backfiring.
How does GunOps work?
GunOps is a web-based application accessed through any computer or hand-held device and lets users enter data on gun related cases with ease. Investigators can then readily search for and visualize the relationships between cases in terms of time, proximity, and firearm evidence characteristics. GunOps has a powerful, yet clean architecture which manages a large volume of firearms crime data and is completely searchable making it the ultimate time saver. GunOps uses a highly intuitive and interactive GUI that makes it easy to learn and seamlessly incorporate into the daily routines of investigators and analysts.
How does IBIS work?
IBIS captures digital images of the unique markings left on fired bullets and cartridge cases by the internal working parts of a firearm during the discharge process. A unique “electronic signature” is extracted from the digital images then stored in a database. As each signature is acquired and stored the system compares it against the others in the database with lightning speed to determine if there is a potential match indicating that the pair was fired from the same gun. Each pair is given a score and ranked in order of the highest likelihood of a match. IBIS networks like NIBIN can share critical data quickly across jurisdictions.
Who uses ShotSpotter?
ShotSpotter is used in approximately 90 cities worldwide. It is highly regarded by law enforcement agencies as a critical component of their gun violence reduction strategy. ShotSpotter deployments include a diverse set of cities by size, geography and socioeconomic standards. Police departments are the typical core user of ShotSpotter, and the data has been shown to be valuable to prosecutors in court cases and city leadership for smart city initiatives.