Comparison of the m = 1 high-latitude mode oscillations in the line-of-sight Doppler velocity as viewed from the Earth, obtained using various methods, when the solar tilt angle B₀ is 7.24° (top), 0° (middle), and −7.24° (bottom). Left column: observed Doppler velocity V_los from HMI data band-pass filtered around ${\nu }_{HL1}^{\mathrm{synodic}}$ ($V_{\mathrm{los}}^{HL1}$, see Eq. (8)). For a better comparison with the middle column, the images were Gaussian smoothed with a FWHM of 5°. Middle column: reconstructed V_los, obtained by projecting the 5°-tile horizontal flow maps from the HMI ring-diagram analysis onto the line of sight and applying the same filter as in the first column. Right column: line-of-sight projection of mode eigenfunction obtained using a linear eigenvalue solver (Bekki et al. 2022), scaled to an amplitude comparable to the observations. Bottom row: maps of noise in $V_{\mathrm{los}}^{HL1}$ estimated from the temporal variance of the data at each spatial point.