Gaia DR2 ϖ of YSOs with IR-excess in Orion A versus l (top, σ_ϖ as error-bars), and projected YSO distribution displayed on the Herschel map (bottom). Red are YSOs that pass the applied selection criteria as discussed in the first two steps in Sect. 2. The blue sources represent the sources lost when the flux-excess-cut is applied. This highlights that nebulae (near the ONC, see map) cause additional ϖ uncertainties, not reflected in σ_ϖ. The 1D distribution of ϖ for both samples is shown in the histogram on the right. The red and blue middle lines show the median ϖ of the samples. The lower and upper borders (black dashed lines) indicate the applied distance cuts to avoid possible foreground or background contamination when deducing the average distances. The middle gray line shows the distance to the ONC of 414 pc (Menten et al. 2007), while the gray shaded band represents the 2D projected size of the cloud of about 40 pc at 414 pc.