Graphical representation of the spherical harmonic coefficients and their covariances. This plot corresponds to the magnetic field reconstruction results in Fig. 4. a) Covariance matrix with the three groups of spherical harmonic coefficients, α, β, γ, stored sequentially in the order of increasing l and m numbers. Dashed lines highlight parts of the covariance matrix corresponding to each group of harmonic coefficients. b) Mean value of the spherical harmonic coefficients. c) Standard deviation of the spherical harmonic coefficients.