Geodesy provides, with state-of-the- art measurement tools, the scientific basis of Navigation, e.g. by the exploitation of the existing and planned Global Navigation Satellite Systems (GNSS). The link to fundamental Astronomy is via the global terrestrial reference system, by monitoring the rotational motion of our planet, by space geodetic techniques, and by establishing the celestial reference system and Univeral Time (UT) reflecting Earth rotation. New frontiers of Earth science knowledge are being explored, such as temporal variations of positions and gravity (land deformations, post-glacial rebound, sea level rise, etc.).