GNSS: A revolution for precise geopositioning.

Global Navigation Satellite Systems (GNSS) were not initially designed to be used for precise scientific applications. However, a smart signal processing can provide a satellite–receiver range measurement with millimeter accuracy. If the differential technique has become an essential method, the PPP mode is today an increasingly popular alternative. But, whatever the approach, GNSS have revolutionized the realization of space and time frames and the many applications requiring post-processed or real-time precise positioning. [ABSTRACT FROM AUTHOR]