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Anti-intruder port protection “MAC (Magnetic ACoustic) System”: advances in the magnetic component performance
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Abstract
In the following, we report the advances made in the development of a magnetic
component for peripheral monitoring of port environments for anti-intruder
systems. The project was initiated by the Office of Research and Development,
COMFORDRAG, Italian Navy, in 2004, with the aim of improving the detection
performance of current acoustic-based anti-intruder systems, in the vicinity of
quays or the seabed or in acoustic-shadow zones behind natural or artificial objects.
In the five-year period from 2004 to 2008, the system has been subjected to
detection-performance tests in experiments involving divers equipped with air tanks
and rebreather kits in real port environments and, at the same time, the associated
signal processing has been subjected to development, to enhance detection
performance. In tests involving simulated diver attacks against a vessel moored
alongside a quay in the port of La Spezia, the system has been proved particularly
effective by detecting 9 divers out of 9. The processing of the magnetic signal has
been enhanced by implementing an amplitude threshold, as a means of filtering the passive energy components, termed Passive Energy Cutting (PEC), that is, the
elimination of components that comprise no useful information regarding diver
transits. The use of PEC boosts the reliability of the system in terms of detection
versus false alarm rate, as evidenced by the comparison of the ROC curves for the
system with and without PEC