Current operations have reaffirmed the need to provide "dismounted personnel" with a means to rapidly pinpoint the source of incoming, hostile, high velocity fire. To do so demands personal equipment that delivers an accurate and near-instantaneous response while at the same time being compact, lightweight, durable and inexpensive.
To address this not insubstantial challenge, Ultra Electronics Sonar Systems has developed a self-contained Gunfire Locator (GL) that leverages the company's deep expertise in acoustics technology to deliver enhanced personal situational awareness to the individual on the ground. Nurtured through the UK Ministry of Defence's 'Competition of Ideas' (CoI) initiative and urgent operational requirements, the focus has been to attach the GL to the personal weapon, normally the rifle (the Rifle Mounted GL - RMGL). The utility could also apply to a full range of optics, cameras and robots.
Although RMGL is by no means the first or only gunfire locator system to come to market, Ultra believes that its technical approach founded on proven techniques adapted from underwater acoustic signal processing offers significant advantages as well as its independent, and therefore flexible, profile for current and future wider use. In addition, this same technology has the potential for further exploitation as part of a networked capability.
The technical challenge that Ultra set out to address in the 'CoI' programme was to accurately measure the direction of gunfire blast and shock pulses using a small sensor, and then present the hostile fire information of range, direction and elevation in a userfriendly format that intuitively directs aim to the source of fire.
Small and medium calibre weapons generate characteristic acoustic signals on firing. The GL derives the direction of hostile fire by applying frequency-domain signal processing techniques to measure the phase shifts between transducers fitted in a golf ball size detector array of transducers mounted on the rifle or sight. In order to accurately fix the firing position and minimise false alarms, including outgoing fire from friendly weapons, an advanced algorithm is used to isolate the source of hostile fire. The GL now demonstrates excellent performance in tests within the operational rural and urban environments characterised by high background noise and reverberation effects.
Mounting the RMGL on the weapon gives the ability to align the display and rifle directly with the target. A clock face indicator arrow display clearly points to the direction and range of the firing point, updating continuously as the weapon is slewed to ensure alignment with the target and the system compensates for a moving individual with a miniaturised three-axis inertial tracking system. If located in urban, hilly and mountainous environments, the GL offers the facility for direction and elevation with a cross-hairs target indicator. The arrow changes to cross-hairs when the weapon is aligned within 30 degrees of the target. Ultra also provides the option of an audible cueing prompt. A simple menu function, accessed using two-button control, enables rapid set-up and the adjustment of operating modes and parameters:
- No calibration is required
- The number of detected shots and the range of the most recent shot are both displayed numerically
- A battery icon is also provided to indicate remaining power (the system uses two lithium AA cells providing up to 7 hours battery life)
- The display brightness can be adjusted according to the prevalent lighting conditions. A red light mode provides for compatibility with night vision systems.
- The basic RMGL equipment is fitted with a data port
Lightweight, rugged and waterproofed, the full RMGL system weighs just 500g and is configured to fit on any infantry weapon by means of a Picatinny Rail or suitable fixture point. A quick release mechanism ensures that the system can be easily detached from the host weapon.
RMGL prototype systems have been subject to extensive trials and evaluation by UK and US defence research communities in a range of operational environments. These live fire events have proved system effectiveness against high velocity fire from 5.56 mm, 7.62 mm (long and short) and 12.7 mm weapons, with the RMGL achieving at least a nominal accuracy of +/- 5 degrees in azimuth and elevation, and 15% in range. Trials analysis has also shown greater than 90% probability of correct detection and localisation of hostile fire.
Development work is continuing, both on the physical sensor and on the signal processing algorithms to improve the performance of the GL unit in difficult acoustic conditions. Efforts are also underway to reduce system size, weight and power consumption. Improved software and increased sensitivity could open the way to expanded functionality for enhanced detection and identification. For example, the display may prioritise heavy calibre threats or another use may be just to listen. In parallel, Ultra is examining other applications for its generic acoustic gunfire location technology. The "mobile static utility" with multi systems linked to a lightweight command cell with underlying mapping will enhance location, protection and hostile detection. Ultra has already undertaken initial work to exploit the technology for helicopter Hostile Fire Indication purposes and is pursuing a funded acoustic locator research programme for the detection of direct fire low velocity projectiles (RPGs) in complex environments. GLs mounted on vehicles, boats, ships, and hovercraft will develop and so will the networked GPS capability to address situation awareness requirements. A networked system could also be synchronised to operate in conjunction with a range of sensors, with weapons if appropriate.
The wider utility of acoustic locator technology and the Ultra GL System extends well outside the military arena. It may include stadium and event security, VIP protection, and 'focused' security offerings to both the public and private sectors.
