Metrology and general relativity

The accuracy of the measurement of time has led to a reconsideration of metrology in the framework of general relativity. This theory, which up to now has passed successfully all experimental tests, keeps the invariance of physical laws, but restricts it as a local property. However, the main applications of the time standards involve a large extension in space: the whole Earth, the solar system and farther. For example, one of the most striking applications is the development of satellite positioning systems that everyone uses: such systems would not operate without a rigorous relativistic treatment. The role of measurements in extended spatial domains is therefore examined. To cite this article: B. Guinot, C. R. Physique 5 (2004).