If you even occasionally enjoy surfing the Web, there is a good chance that you have visited the Google Earth site (http://earth.google.com). There seems to be a certain universal appeal to viewing Earth from the edge of space, selecting a point of interest, and zooming in until objects as familiar as the flowerbeds in your own yard become visible. Imagine then how appealing it would be for Earth scientists, who devote their careers to studying the evolution of the planet’s surface—by examining processes as diverse as erosion, uplift, tectonic-plate motion, seismicity, and volcanism—to have access to a similar resource, but one that offers accurate three-dimensional coordinates of closely spaced points covering any area of Earth’s surface.
The measurements necessary to develop a scientifically rigorous version of Google Earth are the province of geodetic science, or geodesy, a branch of applied science that deals with measuring Earth’s size, shape,...
