Comparison with previous models. Top left: spiral segments (olive) over-plotted on Cepheids identified as members of a group. Groups are color-coded as in Fig. 7. Top right: spiral segments and the model of Reid et al. (2019). The spiral arms delineated by Reid et al. (2019) are over-plotted using the same color-coding as in the original paper. Bottom left: spiral segments and the model of Levine et al. (2006b), with the same color-coding as in Reid et al. (2019). Bottom right: spiral segments and the model of Hou (2021), with the same color-coding as in Reid et al. (2019).