Sonardyne International Ltd has added a new diver interception tool to the capabilities of its Sentinel Intruder Detection Sonar (IDS). The handheld Bearing and Range to Target (BARTT) mobile phone application can be used to provide security boat crews with guidance to the position of an underwater intruder being tracked by the Sentinel system. Information is supplied to the crew via simple, clear graphical and textual displays on a large touch-screen smart phone. The data is provided via a GPRS connection with the Sentinel command workstation and so provides a vital link to ensure that once detected, intruders can be deterred or apprehended.

Sentinel IDS systems are operational worldwide protecting both commercial and military assets, critical energy and civilian infrastructure, VIPs and maritime borders. The system uses advanced sonar technology to provide a 360 degree, below water protection zone that can discriminate between genuine targets such as divers and swimmers and non-threats such as large fish or pleasure craft. Sentinel has been designed specifically for ease of use by security personnel and to meet the practical requirements of everyday use.

A Sonardyne Sentinel may be deployed from a vessel by lowering the compact sonar head into the water from a boom or through a dedicated hull opening. It is also widely used when mounted on a seabed frame to create a permanent installation for monitoring a port entrance, for example. When coverage of larger areas is necessary, up to 10 Sentinel heads can be integrated and they will alert security personnel if any divers come within an 500 metre radius of a sensor.

The new BARTT application is considerably more effective and secure than tradtional guidance provided over radio. From the main Sentinel command workstation, the security operator simply clicks on the intruder track and selects it to be intercepted. The track position data is then automatically transmitted to the BARTT-enabled smart phone carried by the interception team. The mobile device then uses its own position calculated by its built-in GPS receiver to calculate range and bearing to the intruder. This updates continuously as the patrol boat approaches the intruder’s position. The mobile device also sends its own position back to Sentinel where it is displayed on the command workstation. The Sentinel operator can, in this way, monitor the movement of both the target and the intercepting vessel.

The Sentinel Performance Indicator (SPI) is a further new enhancement that introduces software that can provide essential information about the predicted performance of a Sentinel IDS. It informs the operator of the sonar’s operating range by taking account of the environmental conditions at a specific deployment site. It incorporates a high frequency shallow-water sonar performance model, that takes account of background noise and reverberation plus sound speed through water. These can predict the signal variations and the probability of detecting a target. The SPI Operator version of the new software is designed to give a ‘range of the day’ at a specific deployment location. This version requires the minimum of inputs from the sonar operator and produces a coloured contour plot showing signal range and target depth and is very simple for the sonar operator to interpret. SPI Expert is aimed at more experienced users who may wish to plan a sonar deployment by predicting the performance when the Sentinel is installed in different locations or to understand how the performance may change if the conditions vary over time.

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