Serdjo Kos is a Full Professor (tenured) in Navigation Science at the University of Rijeka, Faculty of Maritime Studies, Rijeka, Croatia. He is a satellite navigation, electronic navigation, astronomic navigation and navigation methods specialist. He holds BSc (1986), MSc (1992), and PhD (1994) degrees in technical sciences, at the mentioned Faculty. Professor Kos is Head of Department of Nautical Science at University of Rijeka, a Fellow of the Royal Institute of Navigation, London, UK, and a Full Member of the European Academy of Sciences and Arts, Salzburg, Austria. He is a Full member of the Croatian Academy of Engineering (Zagreb, Croatia), and Academic member of ATINER, Athens, Greece. The Professor’s specific scientific areas of interest are: GNSS positioning error budget; GNSS and space weather interactions; GNSS ionospheric monitoring; risk assessment of electronic navigation utilization.