For more than a decade, the GNSS Service at the Geodetic Institute of Slovenia has been managing the national GNSS CORS network SIGNAL, and since 2016 also the GNSS part of the national Zero-Order Geodetic Network. During this period, different problems in the operation of CORS networks have been encountered, and much experience in the field of management and quality control of CORS networks has been gained. In cooperation with the Chair of Mathematical and Physical Geodesy and Navigation at the UL FGG and the Surveying and Mapping Authority of the Republic of Slovenia, a research project named The increase of reliability of public GNSS network SIGNAL and combined zero-order geodetic network was carried out in 2018 and 2019. Based on all the experience gained, a methodology for upgrading and improving the current procedures for management of both national CORS networks, with an emphasis on improving operational reliability and the quality control of both networks, was developed. In this article, the results of that project are presented.