The output of the observing system includes as a crucial contribution to Earth science, Earth observations, and, increasingly, society, the global geodetic reference frames. The geodetic observations of the variations in Earth's shape, including the surfaces of the solid Earth, the oceans, ice sheets and terrestrial water bodies, and the kinematic of the surface are key contributions to understanding many geophysical processes. Likewise, observations of the temporal variations in the gravity field are related to mass transport in the Earth system, and particularly the global water cycle, and the geodetic observations inform scientists and in the future also regional water management about changes in the water cycle. Earth rotation is inherently related to the large-scale dynamics of atmosphere, ocean, and solid Earth, and the geodetic observations of Earth rotation changes provide valuable constraints for models of these dynamical processes.