Convergence distance depending on noise level. The maximum y-distance dy between starting position and dipole position, at which for 100 random noise distributions the dipole could still get localized, is plotted. We used the inner moments up to the 3rd order , , plotted in curves 3χ and the inner moments up to the 4th order , , , plotted in curves 4χ. The outer moments which were used to model the disturbing fields were none (curves χ0), 2nd order moments (curves χ2: homogeneous fields), 2nd and 3rd order moments (curves χ3: homogeneous and gradient fields), and 2nd to 4th order moments (curves χ4: external fields up to 2nd order). The dipole field of a dipole with a strength of 20 Amm2 at position (x, y, z) = (0, 0, -300 mm) is superimposed by white, Gaussian distributed noise given in fT and as the signal to noise ratio (SNR).