Distribution of EW_862.1 in the Galactic plane (XY), meridian plane (XZ), and rotational plane (YZ) for the FPR results (left panel) and the DR3 results (right panel), respectively, plotted over the Milky Way sketch created by Robert Hurt and Robert Benjamin (Churchwell et al. 2009). Some log-periodic spiral arms described in Reid et al. (2019) are also presented by coloured lines: Scutum-Centaurus Arm in orange; Sagittarius-Carina Arm in purple; Local Arm in black; Perseus Arm in green; Outer Arm in cyan; and the spur between the Local and Sagittarius-Carina arms in blue. The Galactic centre is located at (X, Y, Z) = (8.15, 0, 0).