Estimating Magnetometer Position and Orientation at Extended Distance from the Calibration Coil Array in a Magnetically Shielded Room

We investigate methods for estimating the positions, orientations, and sensitivities of magnetic sensors using multiple coils with known properties, a process we refer to as calibration measurement. In conventional calibration conducted inside a magnetically shielded room (MSR), a systematic estimation error was observed when the distance between the sensors and the coils was increased. This error was caused by demagnetizing fields resulting from the high permeability of shielding materials used in the walls, floor, or ceiling of the MSR. In this study, we propose a new calibration approach that incorporates an approximate model of the demagnetizing field induced by such materials. The effectiveness of the proposed method was validated through two types of model experiments: a simplified setup and a practical setup. The results demonstrated that, even when the sensors and coils were placed farther apart from each other within the MSR, the proposed method effectively reduced the systematic estimation error by accounting for the influence of the demagnetizing field.