Geodesy is a branch of geophysics that studies the geometrical, structural, and gravitational properties of the Earth, their time evolution, and the dynamic interactions of the solid Earth with other physical components of the Earth system (atmosphere, hydrosphere, cryosphere, and the cores), at a wide range of temporal and spatial scales. Geodesists also study the corresponding topics for other planets in the solar system.

Observations and measurements are at the heart of the geodetic science. Those of the static earth using terrestrial and astrometric techniques have been made by humans for many centuries ever since antiquity to understand the size, shape, and motion of the Earth. In the last half century, space techniques have revolutionized the research and applications of geodesy, hence the term space geodesy. Notable techniques include satellite laser ranging and Doppler tracking, very long baseline interferometry, the Global Positioning System (GPS), radar and laser/lidar altimetry, and more recently, synthetic aperture radar, yielding precise information on the Earths surface deformation, gravity field, and variations in gravity, in rotation, and in sea level and ice surface. These observations are key to understanding the geophysical and climatic interactions within the complex Earth system. In this process, geodesy, an oldest human endeavor, has transformed into a most interdisciplinary branch in all of the geophysics today.

AGUs Geodesy Section is proud to contribute to this heritage over the decades, in providing services and fostering interactions among geodesists as well as between geodesists and colleague in other disciplines.

Benjamin F. Chao
AGU Geodesy Section President 2004-2006