Velocity maps for the k ₃ line core (top panels) and k ₂ peaks (bottom panels). The color scale is clipped at −10 km s ⁻¹ and 10 km s ⁻¹ to maximize contrast. The yellow points represent locations where the detection algorithm failed to find the features. The first column shows the atmospheric velocity at the feature's τ = 1 depth. The remaining columns show the velocity shift of the feature as detected from the spectra, for spectra without noise, with noise at S/N of 5, and with noise at S/N of 5 but using a Wiener filter (see the text), respectively.