Olivier Jamet

Biography

Deputy Scientific and Technical Delegate at the Institut national de l’information géographique et forestière (IGN), Olivier Jamet is also a researcher in physical geodesy at the Institut de physique du globe de Paris (IPGP), University of Paris. Until 2018, he headed IGN’s geodesy research laboratory, which is responsible for determining the International Terrestrial Reference Frame (ITRF), and this experience has given him a broad vision of spatial geodesy techniques. In his role as Deputy Delegate, he is particularly responsible at IGN for issues relating to geodetic references, localization and the measurement of deformations.

Conference: Can navigation satellite clocks measure the size of the Earth?

It’s no secret that Global Navigation Satellite Systems (GNSS), including GPS, enable you to locate yourself anywhere on Earth. With professional antennas and a good protocol, you can measure the distance between, say, Paris (France) and Sydney (Australia) with centimetric accuracy. With slightly less stringent precision requirements, anyone can measure the Earth with their own smartphone. These possibilities are based on the very precise dating of signals sent to Earth by GNSS satellites, as well as a good knowledge of their trajectory. Where does all this come from? Can GNSS satellites measure space simply by calibrating their clocks? Using GPS as an example, we will present the basic principles of GNSS precise positioning and discuss its limitations for measuring the Earth. Current methods for calibrating the space scale of these systems will be outlined. The progress made by the European GALILEO system will be discussed.