Cartesian 3D positions and motions of YSOs in Orion A. The scatter plot shows YSOs with measured Gaia DR2 astrometry and APOGEE-2 radial velocities, projected in a Heliocentric Galactic Cartesian coordinate frame (X, Y, Z). The arrows are Cartesian velocity vectors (U_LSR, V_LSR, W_LSR), color-coded for l for orientation (head is yellow, tail is purple). A representative arrow with a length of 10 km s⁻¹ is given in the legend in the X/Y panel. The black arrows in the corners of each panel indicate the line of sight from the sun, pointing toward (l, b) = (211.0° ,−19.5° ) and plotted from d= 325 pc to 340 pc.