Earth's True Shape Revealed for the First Time

After two years in orbit, the European Space Agency’s (ESA) Gravity field and steady-state Ocean Circulation Explorer (GOCE) is nearing the end of its planned life span in February, producing the most accurate map ever of the so-called geoid -- an Earth-encompassing spirit level and global reference surface. An unused supply of xeon fuel will allow the mission to be extended until at least the end of 2012.

Markedly different from a simple sphere or ellipsoid, the geoid is the mathematically 'true' shape of Earth. It represents a motionless global ocean but takes into account the effects of the Earth’s rotation, weight difference resulting from the position of mountains and ocean trenches, and uneven mass distribution and density variations in the planet’s interior.