  In hydrodynamical modeling of heavy-ion collisions, the initial-state spatial
anisotropies are translated into momentum anisotropies of the final-state
particle distributions. Thus, understanding the origin of the initial-state
anisotropies and their uncertainties is important before extracting specific
QCD matter properties, such as viscosity, from the experimental data. In this
work we review the wounded nucleon approach based on the Monte Carlo Glauber
model, charting in particular the uncertainties arising from modeling of the
nucleon-nucleon interactions between the colliding nucleon pairs and
nucleon-nucleon correlations inside the colliding nuclei. We discuss the
differences between the black disk model and a probabilistic profile function
approach for the inelastic nucleon-nucleon interactions, and investigate the
influence of initial-state correlations using state-of-the-art modeling of
these.
