Fig. 5

Comparison of oceanic M2 tide induced magnetic field signal parameters extracted from the residual data by fitting different harmonic sums using an iterative robust least squares approach. The left column shows the extracted amplitudes and the right column the extracted phases in dependence of analysed time series length. In contrast to the previous figures, only the analysis of the first n years of the 10 year time series are presented because of the computational costs of this analysis and the evident conclusions that can be drawn from these presented results. Black lines in the left column show the results obtained by phasing and averaging the residual data and allows for a comparison of both methods. Please note, on the right-hand column the y-scales vary by row. This choice was made to increase presentability of the obtained results. Root mean square values of the residual data for each data point, i.e., for each the fit made with each fit function to the given time span is summarized in the Additional file 1 under Tables S12–S14