April 5, 2011

GOCE Reveals Gravity Map, ESA Conceals It

The ESA has just announced that their GOCE satellite has collected enough data "to map the Earth's gravity with unrivalled precision".  Accompanying the press release was the animation (shown above) of the "geoid" model derived from the new data set.

Unfortunately, the animation lacks the most fundamental feature required of all visualizations: a key to help us make sense of what it actually shows!

The text accompanying the animation sheds a little light on the visualization:
The geoid is the surface of an ideal global ocean in the absence of tides and currents, shaped only by gravity.

If I were to hazard a guess, I'd suggest that the visualization shows the earth's crust, with a height field and colour map applied to it.  The latter two possibly encode the strength of the gravitational field and/or the height of the idealized global ocean (the latter being derived from the former).

The point is I shouldn't have to guess!  This important data deserves better treatment.

If you know what the visualization encodes then please leave a comment below.

[ Update: 8 April, 2011 ]

I had this quick response from the ESA regarding interpreting the Geoid visualization:
The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue colours represent low values and the reds/yellows represent high values.