DWD/Meteorological Observatory Lindenberg is operating a small-scale ground-based network of measurement sites for precipitation and shortwave radiation. The area is located roughly 60 km southeast of Berlin city. 8 measurement sites are equipped with high quality instruments CM21/CM11 by Kipp & Zonen. The quality assessment routinely applied takes into account the basic astronomical and empirical considerations as well as some interdependencies like total to diffuse flux ratio and cross checking with sunshine duration. Possible shading due to growing vegetation is taken into account, too. This is complemented by an approach that is utilizing time-series of clear sky radiative transfer simulations for every site. For that purpose a link to cloud coverage obtained from Meteosat second generation geostationary satellite data, highly resolved in time and space, was established. The paper provides an overview of the surface radiation network and the current activities to improve automatic quality assessment using remotely sensed data and clear sky modelling. First evaluation efforts cover up to 12 years of data.