Method of Magnetic Source Localization Using Gradient Tensor Components and Rate Tensor Components
Patent, Filed 3 Jun 96, patented 7 Jul 98
DEPARTMENT OF THE NAVY WASHINGTON DC
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Method and apparatus for localization and characterization of a magnetic source including source strength and orientation. Samples of five tensor gradiometer signals from a straight-line track are used to construct a polynominial fit to each gradient tensor component with the variable being either time or track distance. Polynominial expressions are used to estimate rate of change of each gradient tensor component at the current sample, providing five numbers. Current samples of the gradient tensor components form a second five number set. An invention inversion process produces solutions for instantaneous bearing vector from the gradiometer to the source, direction in space of the source magnetic moment vector, and ratio of the magnetic moment vector magnitude to the fifth power of range from gradiometer to source from the gradient tensor component rate samples. The process produces one to four solutions for the indicated source parameters, with an additional one to four solutions obtained by reflection of the bearing vector through an origin located at the gradiometer, with the associated moment vector directions remaining unchanged. Solutions resulting are applied to magnetic source localization. Gradient tensor information is independently processed using the Frahm-Wynn inversion algorithm, to produce multiple solutions for bearing vector, direction of the magnetic moment vector, and ratio of the moment vector magnitude to the fourth power of the range. The two solution sets are merged, producing a unique solution for source position vector and magnetic moment vector for each successive location of the tensor gradiometer.
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