Case study of June 25, 2020: Spectrograms of the wave parameters calculated on the ground from the snapshots of waveform, for the same time interval and frequency range as in Fig. 6, and with the same format as in Fig. 3, except for the last two panels where the second method of phase velocity measurement (as given by Eq. (16)) is used instead of the first one, as given by Eq. (13). Again, only cases matching DOP ≥ 0.9 are displayed. The strong spurious vertical lines already observed in the magnetic power spectrograms of Fig. 6 are still visible here in the top panel (PB), as well as in all others, as spurious coherent vertical lines.