GNSS signals: a powerful source for Atmosphere and Earth's Surface Monitoring

It is well known that Global Navigation Satellite Systems signals (which include for example the U.S. GPS and its modernization, the Russian GLONASS, the future European Galileo, the Chinese COMPASS), commonly processed for navigation purposes, can also be used to characterize media where they propagate in. In the last decade, GNSS atmospheric and Earth’s surface remote sensing become more and more important, thanks to technical improvements applied to the processing of such “free-of-charge”, everywhere available and weather insensitive signals.