A Novel Method for Magnetic Anomaly Localization and Magnetic Moment Orientation Estimation Using a Three-Axis Fluxgate Sensor

Using the simplest sensor setup to achieve magnetic anomaly localization and magnetic moment orientation estimation is significant in magnetic anomaly detection. This paper presents a novel approach using a single fluxgate sensor to accomplish this goal. In the proposed method, the number and horizontal positions of magnetic targets are determined by 2D constant false alarm rate (2D CFAR) detection applied to pseudo <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> norm energy. The remaining parameters are then estimated by minimizing a pseudo <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> norm energy loss function. Compared with fixed-threshold detection, this method achieves 2D dynamic threshold detection, effectively mitigating the risk of missing low-energy targets. Unlike traditional magnetic anomaly-based optimization, this method innovatively performs inversion in energy domain, significantly enhancing noise resilience. Moreover, it keeps the number of optimization parameters constant as target count increases, avoiding the accuracy deterioration commonly associated with parameter growth. In Monte Carlo comparison experiment at 20 nT noise level, the proposed method outperformed the total magnetic field 2D orthogonal basis function method, achieving approximately 59 and 81% improvements in the root mean square error of horizontal localization and false alarm rate, respectively. Single-target simulations demonstrated the effectiveness of the proposed method, while multi-target simulation confirmed its robustness. The signal-to-noise ratio (SNR) of total energy exhibits a 25.51 dB improvement over the average SNR of magnetic anomaly components, underscoring strong noise suppression capability. Field experiments involving both single and multiple targets yielded results consistent with simulations, further validating the method’s practicality.