Measuring instrumentation in magnetic silencing: orthonormal discrete transforms of magnetic signatures

Magnetic multipole imaging is an approach to a compact description of the magnetic source. Particularly noteworthy are the magnetic measuring techniques aimed at recognition, identification and modelling of these field sources. Historically, applications of the multipole imaging have been made to the terrestrial magnetism. Shipboard-type electrical equipment can additionally generate permanent or low frequency external magnetic fields. In a variety of applications, it is desirable to reduce the total external level of the field produced by vessel. For example, this level affects the vulnerability to detection and recognition. Since multipole image (MI) encapsulates all the main features of a magnetic source, its processing has received increased attention as an approach to both a morphological analysis and spatio-temporal modelling of magnetic fields. Multipole imaging provides a high-speed computational tool for the classification and comparison of objects by their actual 3D magnetic fields. With static multipole imaging techniques, field data are received while the relative position of the sensors and the test object is fixed. In dynamic analysis, the sensors move relative to the test object, so that the sensors trace also forms a virtual image surface. This recorded magnetic image is traditionally called magnetic signature (MS). The dynamic MI estimation methods provide a self-adjustment technique. This is important in the identification of unknown sources, where the highest order of the MI can not be predicted before the test. Furthermore, the dynamic procedure is the most effective technique for independent objects and therefore is the most practicable in magnetic silencing of sweepers, underwater vehicles and geophysical research ships. This work presents a novel technique that improves the performance of magnetic signature processing and multipole imaging in magnetic silencing of vessels