Magnetic Gradient for Target Localization at Point of Close Proximity Approach

Magnetic anomaly generated by a magnetic target is widely used in many areas. The target can be located by using the magnetic anomaly. To decrease the complexity of nonlinear function solution when locating a target, we propose an effective method for target location using the close proximity approach (CPA) point on the trajectory, which is the closest point from the target to the trajectory. According to the properties of the magnetic gradient at the CPA point, we derive the expressions for the target position and its magnetic moment at the CPA point. The position and magnetic moment at each measurement point can be easily calculated in real-time using the expressions. Meanwhile, we also introduce an error index that can be used to determine the CPA point, which is a key factor for obtaining the position and moment of the target along the trajectory. Based on the CPA point determined by the index, the position and magnetic moment of the target can be easily obtained. The proposed method is validated through simulation and experiment. The results demonstrate that the CPA point can be easily determined, and the distance error between the target and the sensor array is less than 10% at the CPA point. The localization accuracy of the proposed method is relatively high. Therefore, the method has significant potential for target localization in mobile magnetic anomaly detection (MAD) systems.