A novel 3D target location method using 2D orthonormal basis functions of total vertical gradient of magnetic anomaly

Magnetic anomaly detection (MAD) has been recognized as an effective method for detecting and positioning magnetic targets. To address the issue of scalar MAD being influenced by the magnetic moment orientation (MMO) and the challenge of estimating the vertical coordinates of the target, a three-dimensional (3D) target location method is developed in this article. The proposed method first employs the total vertical gradient of magnetic anomalies to characterize their spatial distribution and constructs a two-dimensional orthonormal basis functions (VG-2D-OBFs) model to represent these properties. Then, by employing a black-body model to decouple vertical and horizontal localization, this approach reduces the complexity of the solution while enhancing depth estimation accuracy. Ultimately, a 3D target localization framework is developed, utilizing a two-step strategy to enhance spatial accuracy. Simulations and field experiments demonstrate that the proposed method not only has good robustness and high positioning accuracy, but also is insensitive to the magnetic moment orientation, with the root mean square and standard deviation of the localization error for different MMOs reaching 0.149 m and 0.069 m, respectively. Therefore, as a post-processing method, it is of significant in the of detection.