H i line emission (green curve) and absorption (violet curve) spectra against (a) G46.8–0.3 SNR and (b) G046.495-00.241 H ii region. The solid vertical line in each panel marks the velocity of the tangent point at the longitude of the sources according to the Reid et al. (2014) Galactic rotation curve, whereas the dashed vertical line in panel b is for the hydrogen RRL at 58.4 km s⁻¹ from G046.495–00.241 recorded in Liu et al. (2019). The horizontal shaded regions indicate the rms noise level of ~4 K in the H i absorption spectra.