Application of Helbig integrals to magnetic gradient tensor multi-target detection. (15th August 2022)

• Record Type: Journal Article
• Authors: Li, Qingzhu; Li, Zhining; Shi, Zhiyong; Fan, Hongbo
• Is Part Of: Measurement. Volume 200(2022)
• Publication Date: 2022-08-15
• Subjects: Magnetic gradient tensor -- Helbig integrals -- Magnetization direction estimation -- Invariant improved tilt angle -- Multi-target source positioning; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2022.111612
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: We extended the magnetic gradient tensor Helbig integrals (MGTHI) from the classical Helbig integrals (HI), so that the advantages of the magnetic gradient tensor (MGT) can be applied to the method. The two-dimensional trapezoidal rule method can be used to estimate the MGTHI well, and help to find the total magnetization direction and horizontal positions of multiple targets. The invariant-improved tilt angles can well identify the distribution area and number of multiple targets, and further improve the positioning accuracy. Magnitude magnetic anomalies and their transformation variables are used to estimate buried depths and magnetic moment magnitude of multi-target objects. Abstract: We extended the magnetic gradient tensor Helbig integrals (MGTHI) from classical Helbig integrals (HI), which can be perfectly adapted to the grid measurement of planar-cross magnetic gradient tensor system. With different sizes of windows, we can estimate the MGTHI by using the two-dimensional trapezoidal rule algorithm and calculate the total magnetization direction of grids, where the node with the smallest change in the magnetization direction is target horizontal position. In the targets recognition area determined by the invariant improved tilt angles, the source depth and dipole moment magnitude can be calculated with magnetic vector and tensor field data directly above the source. In experiments, the horizontal position deviation of multiple small magnets in the survey area of 2.1 m × 2.1 m and 1.2 m × 1.2 m is less than 0.08 m, and the buried depth deviation is less than 0.15 m, the positioning accuracy is improved by more than 5 times from the classical HI method.