Earth's True Shape Revealed for 1st 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.

The resulting small variations in the Earth’s gravitational field feature on the geoid as ‘bulbs’ and ‘dips’ in an idealized ‘ocean’ surface.

ESA scientists presented the latest version of the GOCE-derived geoid map – based on eight months of data processed so far – at a user workshop this week in Munich, Germany.