From historical GPS to GNSS: use for high-precision positioning

GNSS (Global Navigation Satellite System) has become a fundamental positioning tool since the beginning of the 21st century. Initially, use began with GPS, developed by the American army in the 1970s, and became truly operational (industrialization of receivers, number of satellites in service, etc.) in the early 90s. Other space systems of the same type - Russian (Glonass), Chinese (Beidou/Compass) and European (Galileo, the only purely civilian system) - have also become fully operational.

Today, GNSS is a positioning system used by a wide range of technical users (aerial navigation, car navigation, surveyors' work, civil engineering, etc.), but also and above all by the general public (a GNSS receiver is often included in cell phones: pedestrian guidance, photo location, car navigation, etc.). GNSS accuracy ranges from centimeters to several meters, depending on the technology used.

This article presents the uses of GNSS for high-precision measurements, hitherto limited to purely professional contexts, but which are now becoming accessible to the general public. The history of satellite positioning is first used to understand the current situation and anticipate that of the coming decades. Problems arising from the use of various reference systems are discussed, and measurement procedures, different types of equipment and limitations of use are analyzed. A typical illustration is presented, that of the auscultation of an engineering structure.