Method for analyzing magnetic detection blind zone

Patent metadata

Field	Value
Publication number	US-11460518-B2
Application number	US-202016848787-A
Country	US
Kind code	B2
Filing date	Apr 14, 2020
Priority date	Apr 15, 2019
Publication date	Oct 4, 2022
Grant date	Oct 4, 2022

Abstract

Disclosed is a method for analyzing a blind zone of a magnetic detection method that can provide a complete distribution map of the detection blind zone within the entire zone of the magnetic target. The method comprises the first step of establishing a complete magnetic detection model to obtain calculated position and magnetic moment of a magnetic target that is detected by a magnetic gradiometer. The second step involves establishing a direction-attitude-sphere model to represent the entire zone of the magnetic target. The third step involves expanding the direction-attitude-sphere to a planar map layered by latitude and calculating success detection rates within the planar expansion map. Finally, the distribution map of the magnetic detection blind zone in the entire zone is visually presented in the planar expansion map and a complete distribution rule of the entire detection blind zone is thus obtained. This blind zone analysis method is applicable to any magnetic detection method and can provide a visual presentation of the entire detection blind zone. The knowledge of the detection blind zone can be applied to guide practical magnetic detection to avoid the detection blind zone so as to increase the detection accuracy.

First claim

What is claimed is:

1. A method for analyzing a magnetic detection blind zone, comprising the following steps:
a, establishing a complete magnetic detection model to calculate position and magnetic moment of a magnetic target as detected by a magnetic gradiometer comprising multiple magnetic sensors, which comprises the steps of: 1) establishing a magnetic target model based on magnetic dipole model to obtain a magnetic field {right arrow over (B o )} generated only by the magnetic target; 2) superposing a noise signal generated by the noise model No(μ,σ 2 ) onto the magnetic field {right arrow over (B O )} to obtain a superposed magnetic field {right arrow over (B r )}; 3) establishing a magnetic sensor model based on the sensitivity of the magnetic sensors and using the magnetic sensor model to perform data processing on the magnetic field {right arrow over (B r )} to obtain output values of the magnetic sensors, {right arrow over (B S )}; 4) establishing a tensor model based on the structure of the magnetic gradiometer that is used for the magnetic detection and using the {right arrow over (B S )} as inputs for the tensor model data processing to obtain an output value of the magnetic gradiometer, {right arrow over (G)}; 5) establishing an inversion model based on the magnetic detection method and using the {right arrow over (G)} as an input for the inversion model data processing to obtain calculated position and magnetic moment of the magnetic target;
b, establishing a direction-attitude-sphere model of the magnetic target to represent the entire zone of all possible positions and attitudes of the magnetic target, wherein the attitude of the magnetic target is represented by its unit magnetic moment vector {right arrow over (m 0 )}, the direction of the magnetic target is represented by its unit position vector {right arrow over (r 0 )}, and an included angle between {right arrow over (m 0 )} and {right arrow over (r 0 )} is ϕ, wherein a direction-sphere is formed by making {right arrow over (r 0 )} cover the entire direction-sphere, wherein for each {right arrow over (r 0 )}, there is an attitude-sphere formed by making {right arrow over (m 0 )} cover the entire attitude-sphere, and wherein the coordinate system of the direction-sphere coincides with the coordinate system of the magnetic gradiometer, and the axis z′ of the coordinate system of the attitude-sphere and {right arrow over (r 0 )} are aligned on the same straight line;
c, dividing the surface of the direction-attitude-sphere into meshes of an equal size so that each detection condition is represented with equal probability, and expanding the meshes into a plane layered according to their latitude, wherein N is the number of meshing layers, i and j are the number of meshing row and meshing column, respectively, and wherein the latitude (La(i,j)) and the longitude (Lo(i,j)) of a mesh with the mesh row number of i and the mesh column number of j are given by the following formula:

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Assignees

• Pan Donghua
• Lin Shengxin
• Jin Yinxi
• Li Liyi
• Harbin Inst Technology

Inventors

• Pan Donghua
• Lin Shengxin
• Jin Yinxi
• Li Liyi

Classifications

• G01V3/081

  the magnetic field is produced by the objects or geological structures (characterised by the method of magnetic field measurement G01R33/00) · CPC title

• G01R33/022 Primary

  Measuring gradient · CPC title

• G01R33/0029

  Treating the measured signals, e.g. removing offset or noise · CPC title