Distance probability density function for G019.60-00.23, a 22 GHz water maser at v = 47 km s⁻¹ from the Valdettaro et al. (2001) catalog. The (l, b, v)_src values most likely associate it with the near portion of the Scutum spiral arm (at 3.3 kpc), although the Norma arm (at 5.4 kpc) and the far portion of the Sagittarius arm (at 12.9 kpc) are not ruled out (red dashed lines). However, the combination (solid black line) of arm assignment probability with the kinematic distance (green dotted–dashed line), latitude probability (cyan dashed line) and association with a parallax source (blue dotted line) strongly favor a distance of 3.38 ± 0.19 kpc.