Magnetic Dipole Target Two-Point Positioning Method Based on Tensor Invariants

Magnetic anomaly detection (MAD) technology based on magnetic gradient tensor (MGT) holds great potential for applications in unexploded ordnance detection and underwater moving target tracking. The existing inversion methods are highly susceptible to the effects of geomagnetism, environmental noise, and measuring point distance. To address these problems, this paper presents a novel two-point method for dipole target positioning based on tensor invariant theory. First, the geometric relationships between the target and measuring points are derived utilizing the tensor invariants at two measuring points, and four equations containing the target position parameters are established. To improve the noise immunity, an objective function is constructed, and the solution of the target position is transformed into an optimization problem. Moreover, to analyze the positioning effects and blind spots of the method, a simulation model is designed. Simulation results indicate that the method exhibits excellent positioning performance on the entire trajectory and eliminates the effects of the geomagnetic field and measuring point distances to the greatest extent. Finally, the applicability of the method in both stationary and moving target positioning scenarios was validated through field experiments. The average relative positioning errors for stationary and moving targets are 10.57% and 7.59%, respectively, which are lower than the state-of-the-art method.