The increasing availability of affordable hardware for global navigation satellite systems (GNSS) and open-source software for GNSS data processing is shaping geoscience research in novel ways. By using these technologies, researchers can now perform highly accurate positioning and data analysis at a fraction of the cost of geodetic quality hardware and software. Given that positioning, reflectometry, radio occultation, space weather monitoring, and atmospheric sounding with GNSS have become operational techniques, and new experiments are being conducted with low-cost GNSS hardware and open source GNSS processing software, it augurs well for the geosciences at large to exploit these developments for furthering our understanding of the Earth system. In this session we solicit abstracts on use, development and novel geoscience applications of low-cost GNSS hardware and open source GNSS software. In addition, we welcome other contributions highlighting the opportunities and challenges in using low-cost GNSS hardware and open source GNSS software.