In this contribution, we show, that the evaluation of electronic transport parameters in confined systems can be considerably improved by additional Scanning Tunneling Microscopy (STM) imaging of the limiting surfaces. The thin films which are experimentally available usually show both a mesoscopic and a microscopic (i.e. atomic) surface roughness. These two roughnesses, however, are of well separated magnitudes and therefore can be treated either by classical averaging or by quantum mechanics. In order to ensure reliable STM results, the resolution especially of mesoscopic surface features will be discussed. Provided reasonable STM resolution, the experimental data for the resistivity can be interpreted for the first time with a realistic, two dimensional model for the current transport in thin films. Forthcoming applications concerning the distribution of the potential related to current transport in thin films will be discussed.