Modeling of observed spectral line profiles relies on the chosen parameterization of the physical parameters, approximations employed to solve the radiative transfer equation, and atomic data. The implicit assumption in all inversions is that atomic data are correct and known well enough to provide reliable physical parameters. Using poor atomic data significantly hinders our inversion results, especially in the case of multi-line inversions. In this talk, I will talk about a method for a self-consistent inference of atmospheric and atomic parameters from spatially resolved multi-line observations. I will highlight the robustness of the method by applying it to observations from the GREGOR/GRIS at 1.56 microns. Additionally, I will show some preliminary results from an inversion of a SunriseIII/SUSI observation of the quiet-sun at 409nm.