Clearly, there is a well-justified rationale for nations or groups of nations to build their independent, space-based navigation systems. Overall, however, all GNSS in place today can be received and utilized by all interested users around the globe. The larger number of visible satellites is particularly appealing for GNSS radio scientists who aim to derive temperature and humidity profiles from subtle variations in GNSS signals passing through diverse atmospheric regions. All in all, the availability of four GNSS means better performance, robustness, diversity and flexibility for navigation users. Oliver Montenbruck is the head of the GNSS Technology and Navigation Group and Peter Steigenberger is a senior scientist at the German Space Operations Center, German Aerospace Center (DLR).