NEW APPROACHES TO MAGNETIC MODELLING. I: PROLATE SPHEROIDS. II: ONE-SPIKE-AT-A-TIME FITTING

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Authors
  1. Holtham, P.M.
  2. Lucas, C.E.
Corporate Authors
Defence Research Establishment Pacific, Victoria BC (CAN);Barrodale Computing Services Ltd, Victoria BC (CAN)
Abstract
A semi-empirical model is described for parameterizing the magnetic signature of a ship or submarine in terms of a source distribution of independently magnetized prolate spheroids. The magnitudes of the components of the three-dimensional magnetization vectos for each spheroid are determined by fitting to experimentally determined field values. The equations that describe the model are shown to be valid for permanent, induced, and combined sources of magnetization. In a typical application, field values are determined from a degaussing range, and the model is used to predict signatures for mine-simualtion, surveillance or ranging applications. A description is given of the non-unique and non-realistic solution-problems that occur when least-squares methods are applied to supposedly over-determined sets of simultaneous equations which, in fact, are described by a 'rank-deficient' modelling matrix. To overcome these problems, a 'one-spike-at-a-time' technique , first developed for seismic deconvolution, was adapted for use with the magnetic model. Examples are given of fits to simulated data, together with fits to experimentally obtained data for both non-degaussed and degaussed steel-hulled vessels.
Keywords
Magnetic modelling;Least-squares filling;Prolate spheroid modelling
Report Number
DREP-93-81 —
Date of publication
01 Nov 1993
Number of Pages
66
DSTKIM No
95-00109
CANDIS No
147854
Format(s):
Hardcopy;Document Image stored on Optical Disk

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