A new EMAG metrological approach for submarine detection: fundamentals of the numerical protocols and preliminary field performance

Abstract

The characteristics of the geomagnetic field and its artificial components make the capability of reading and classifying large underwater cinematic sources (e.g. submarines) somewhat random. As an example the “ASW far detection procedure” is also affected by the induced magnetic field produced by man-made telluric currents. This could generate some dangerous false alarm. The problem is not an instrumental issue related to the instrument precision of the sensor (commercial magnetometers have precisions greater than the one required by the application) but a classical metrological matter that could be overcome with a correct measurement procedure. This moves the problem from technological to phenomenological aspects. By applying the C.A.I.MA.N. (Coastal Anti-Intruder MAgnetometric Network) experience, inter-nodal distances in the observation chain were calculated so as to correlate the noise and de-correlate the target signal (source type SU.S. "SUbmarine Standard"). By means of C.A.I.MA.N. protocols, targets signal contained in the “detection magnetogram” F(target) was isolated from F(noise+target) magnetogram using F(noise) (that includes also natural variations) as Time-Domain filter, and then submitted to standard LP procedure to increase the information capability. Finally, to overcome metrological problems related to the low incremental ratio [∂F/∂s]ds of the detected signal, we propose a power domain analysis of the detection magnetogram. Also without a dedicated technology, in a preliminary experiment for SU.S. detection the C.A.I.MA.N. anti-intruder system has been occasionally modified: the first results obtained in this study were found encouraging and further detailed investigations within this framework should be undertaken in a future study.