Comparison of EWs (top) and velocities (bottom) measured with the automated technique and a double Gaussian fit for Na I D with the wavelength separation fixed. Each plot shows the corresponding best linear MCMC fit (LINMIX_ERR; Kelly 2007) as a solid orange line and the variance with respect to the fit line in yellow. The x = y line is indicated in dashed green lines. In the bottom plot, the green points show that cases for which the EW/τ_EW > 1.3 and EW > 0.5 have lower uncertainties and agree better within the two methods. The uncertainties here do not include the uncertainty floor of 35 km s⁻¹.