This book collects the proceedings of the symposia held during the 36th IAG General Assembly. This international event, held every fourth year, serves as a forum to announce and record new achievements and the primary research directions of the worldwide geodetic community. The actual date of this assembly, on the verge of the 3rd millennium, adds a particular accent to the results and proposals collected here, which is especially exemplified by the new perspectives derived by the advanced tools and techniques of earth observation from space platforms. Not to be overlooked are the enhanced capabilities of the now classic navigation and positioning systems, under the collective name GNSS. Together with classic techniques like SLR, VLBI, Doris, Prare etc., these provide the capability for establishing a global reference frame at the millimeter level, which currently relates global with regional phenomena of the physics of the earth. In recent years, the surface of the earth has been surveyed with a SAR technique covering all the continents, while the ocean is continuously monitored by new altimetric missions. Furthermore, the gravity field is now measured from space and interpreted in terms of geodynamical phenomena. Even more accurate and high resolution missions are planned, the study of which has already strongly propelled new theoretical achievements in the field of gravity modeling. All this is contained in these proceedings, opening a window to the future of all these promising and exciting developments.