Researchers in the Netherlands have created a ground-based alternative to global satellite navigation systems (GNSSs) – claiming that it could offer a far greater positioning and timekeeping accuracy in cluttered urban environments.The team’s SuperGPS system uses an atomic-clock time signal that is distributed using existing optical and microwave telecommunications technologies.However, for a GNSS to work the device on the ground must be able to receive signals from at least four satellites, which can be difficult when the user is indoors or surrounded by tall buildings.The team say that SuperGPS could benefit a range of applications including automated vehicles, quantum communication and next-generation mobile communication systems.The system could also be used as a vital back-up to existing GNSSs and could form the basis of national timing networks."