Uncertainty in Measurements of the Distances of Scattering Screens in Pulsar Observations

In our previous paper (Popov et al. (2016)) we investigated properties of the ionized interstellar medium in the direction of three distant pulsars: B1641-45, B1749-28, and B1933+16. We found that uniformly distributed scattering material cannot explain measured temporal and angular broadening. We applied a model for a thin scattering screen and found the distances to the scattering screens in all directions. In this paper we consider more complicated models of scattering material distribution, such as models containing both uniformly distributed medium and thin screen. Based on these models we estimate the accuracy of localisation of scattering screens and possible relative contribution of each scattering component.