Notes. Values represent the mean ratio of intrinsic 3D to projected 2D NN separations for a uniform distribution under finite spatial dynamic range (SDR = FoV/FWHM_beam). The tabulated values can be reproduced using the projection_correction(N, SDR) function from the corespacing3d package (Barnes & Henshaw 2026). The second and third rows list the corresponding beam FWHM in arcseconds and physical resolution in parsecs, assuming an ALMA primary beam of 57″ at 100 GHz and a typical clump diameter of 1 pc (distance 3.6 kpc). For large samples (N ≳ 100) and well-resolved maps (SDR ≳ 30), the ratio saturates near 𝒞 ≈ 2.0, whereas poorly resolved or low-N cases converge to 𝒞 ≈ 1, approaching the geometric limit 4/π ≃ 1.27. For reference, an ALMA 100 GHz pointing imaged at 1″ resolution corresponds to SDR ≈ 57, equivalent to a spatial resolution of ~ 0.018 pc for a 1 pc field at 3.6 kpc. The calibration is based on idealised, complete simulations; when applied to real data with finite sensitivity, blending, and N_obs < N, these values should be treated as approximate corrections and, if evaluated with N_obs, as lower limits on the true 3D spacing (see Sect. 5.3).