The invention of Global Navigation Satellite System, GNSS, have entirely transformed the world. These systems include GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), Galileo and Beidou, have become key element in many of widely spread industries, including civil aviation navigation. During the past 4 decades, GNSS has undergone significant technical development, starting from its initial introduction in the 1970s to the current significantly upgraded systems that are being used today. With exponentially improving GNS systems, it has become increasingly important to understand its process of development and its impact on civil aviation navigation. The objective of this thesis work is to provide an overview of general operating principle of GNSS; the first GNSS rated for use during IMC for air operations ; overview and comparison of current GNSS systems and finally future state-of-art GNSS. Additionally, this thesis aims to explore the impact of GNSS on civil aviation navigation, including its challenges, benefits and potential disadvantages and risks.