Different spiral arm models. The top panel is a longitude-velocity view of filaments and spiral arms. Spiral arms from Taylor & Cordes (1993), Reid et al. (2019), and Hou (2021) are plotted as solid lines, dashed lines, and dotted lines, respectively. Red, brown, blue, and green represent the Norma-Outer, Scutum-Centaurus, Sagittarius-Carina, and Perseus arms, respectively. Black circles denote our filaments. The bottom panel is a face-on view of filaments and spiral arms. The cyan plus symbol represents the Galactic center, and the grey dashed lines show the data range.