The geostrophic relationship enables the calculation of ocean surface currents from the mean dynamic topography (MDT). The MDT can be assessed by subtracting the reference geoid from the altimetric sea surface height. Severe problems occur during the determination of the exact geoid, based on different scales and the projection onto a finite grid. New geoid modeling approaches also considering the omission error reveal that even GRACE data are not accurate enough for the purpose of ocean modeling. Especially in polar regions, altimetric measurements may also face problems according to the presence of sea ice. But as sea ice drift is partly driven by ocean surface currents, radar imagery allows for ocean model refinement as well. Clever image processing techniques and reasonable atmospheric (model) data are necessary for this approach. We will present and compare results for a simple section model of the Southern Ocean, give formal error estimates and indicate possibilities for profound model improvement.