So-called complete gravity field models together with their full error variance/covariance information have recently been designed to be integrated into geo-scientific process models. In our case, the ocean's mean dynamic topography (altimetric mean sea surface referenced to the geoid) is used to improve estimates of the general ocean circulation in the context of stationary ocean models. We want to combine complete gravity field models with altimetric data for which a full error propagation is also implemented in the processing. Thus we derive estimates of the ocean's mean dynamic topography with a regular covariance matrix. The goal of this project is to assess the effects of this data combination on improving ocean models. Preliminary results already show that geoid models developed from GRACE data are, while accurate on very long scales, hardly yet accurate enough for that purpose. We anticipate that the increased accuracy, especially on shorter scales, of gravity measurements from GOCE will contribute to a more realistic description of ocean currents as well as mass and heat transports.