A test was conducted at a gun range located at 14750 Skyline Blvd, Los Gatos, CA 95033, to demonstrate the feasibility of detecting gunshot locations using three wireless GRS units. Algorithms of time stamped signal processing were applied to the acquired data, and it was shown that the detection accuracy could be within 1 meter. This test exemplifies the application of GPS time stamping technology.

Equipment provided by Crystal Instruments:

3 sets of CI-GRS data acquisition systems, powered by solar panels
3 microphones
1 drone
1 camera

Equipment and support provided by the gun range:

Exclusive access to the range for 2 hours
Security personnel to ensure site safety
Firearms: Handguns (9 mm and .38 special caliber), a rifle (.308 caliber), operated by range personnel, with a dozen bullets for each handgun and 20 bullets for the rifle

Test Description

Crystal Instruments manufactures the CI-GRS, an acoustic measurement instrument. The objective of the test was to use three GRS units to capture the sound of gunfire and calculate its exact location based on the recorded sound signals. The instruments were placed a few hundred yards apart. During the gunfire, these instruments recorded acoustic data, which was then time-stamped and tagged with GPS location signals.

Operators were required to maintain a distance from the instruments during sound recording, as the operation was fully automated. Four engineers from Crystal Instruments were present at the testing site, with an initial 30-minute setup time for configuring the instruments. Each measurement took 30 minutes, followed by a reconfiguration for the second setup, requiring a total of 2 hours at the testing site.

The sampling rate of GRS was set to 102.4 kHz. Such high frequency sampling is often unnecessary but we simply wanted to demonstrate the data recording capability. Dual ADC technology is incorporated in the instrument design to eliminate any concerns about its overload and gain settings.

A drone was deployed to capture video clips of the test, ensuring the visibility of the three GRS units. Photos and videos were taken, and any areas of concern for the gun range were edited out by Crystal Instruments.

Instrument Setup 1

In the first setup, the three GRS units were positioned roughly 150 to 200 yards apart, forming an equilateral triangle, with the gunfire source near the center. Precise measurements were not necessary.

Recording the Gunshot Location: One GRS unit was positioned at the gunfire location to record the time and GPS coordinates. This recorded location served as a reference to compare with the calculated locations based on acoustic signals.

Instrument Setup 2

In the second setup, the three GRS units were positioned roughly 200 to 300 yards apart, again in an equilateral triangle, with the gunfire source outside the triangle. As in the first setup, precise measurements were not required, as the detected location would ultimately be compared to the GPS measurement of the gunfire source.

Record Gunshot Location

First, position one of the GRS units to the location of gun fire and take a time recording. The purpose of this recording is to record the actual GPS location of the gunshot. This location will be compared with those calculated based on the acoustic signals.

Gunfire Data

Typical data plots of gun shots resemble the following:

They are loud and clear. The recorded data was sent to Crystal Instruments engineers for post processing and cross-correlation analysis using EDM PA to calculate the time delay between each pair of GRS units.

Results and Conclusion

After data acquisition and post-processing with EDM PA software, the gunfire location was displayed on a map. The detection accuracy was found to be within 1 meter of the actual GPS location.

The technology utilized in this test is detailed in a patent application, highlighting its innovative approach to gunfire location detection using wireless data acquisition systems.

Gunshot Location Detection with 3 GRS Units