In this paper, we demonstrate the benefit of using observations from Meteosat Second Generation (MSG) satellites in addition to in-situ measurements to improve the spatial resolution of solar radiation data over Belgium. This objective has been reached thanks to geostatistical methods able to merge heterogeneous data types. Two geostatistical merging methods are evaluated against the interpolation of ground-data onldy and the single use of satellite-derived information. It results from our analysis that merging both data sources provides the most accurate mapping of surface solar radiation over Belgium.