The Geodesy Section is concerned with the study and measurement of the external shape and gravity field of the solid Earth, the oceans, and the major ice sheets, including their temporal variations. The construction of the Earth’s core and mantle as well as the internal dynamics and the exchange of angular momentum between these components are of interest to the section, especially their contribution to changes in Earth’s rotation. Geodetic measurements are crucial to the study of climate change, the advance and retreat of ice sheets and glaciers, sea level rise, and charting the motion of the Earth’s crust through time.
Geodesists are constantly striving for more accurate measurements to complement their existing techniques, and today new, exciting technologies are expanding the possibilities of their research. Space techniques, such as very long baseline interferometry and laser ranging, which chart positions on Earth with unprecedented accuracy have been applied for more than a decade, but Global Positioning System receivers are now being installed for continuous monitoring of crustal motions, especially in seismically active areas. In addition, altimeters carried by satellites and aircraft are being used to monitor ocean topography, including ocean circulation and sea level, as well as variations in the polar ice sheets. The TOPEX/POSEIDON and ERS-1/2 satellites have returned a wealth of information using radar altimetry, and future satellite altimeters will further expand this base.