Yes we can! Barack Obama used this one-liner as a personal war-cry during his election campaign.

Yes we can! replied technicians when questioned about the possibility of taking an image of the inauguration.

And, yes, we can almost count the people at the ceremony thanks to the sub-0,50 metre resolution, colour satellite image of the inaugural celebration.

This spectacular photo shows the National Mall in Washington DC on January 20, 2009, at 11:19 am (EST). It was taken by the GeoEye-1, the world's highest-resolution commercial Earth-imaging satellite. Weighing 2 000 kilograms the satellite was launched from Vandenberg Air Force Base, California, on September 6, 2008.

The GeoEye-1 travels at a speed of 27 000 kilometres per hour and at a height of 681 kilometres. It orbits the poles in a sun-synchronous orbit and at an inclination of 98 degrees, crossing the equator at 10:30am. This synchronicity with the sun means the surface illumination angle is almost the same every time the satellite passes a given point on the earth's surface.

The satellite is able to discern objects on the ground as small as 0,41 metres in panchromatic mode, and 1,65 metres using multispectral imagery in 15,2 kilometre-wide swaths. GeoEye-1can also make images up to 60 degrees off nadir. Due to current US licensing restrictions the panchromatic imagery is re-sampled to half-meter ground resolution. Combining the panchromatic and multispectral images results in full colour images with a 0,50 metre resolution.

GeoEye plans to launch a second satellite, GeoEye-2, with specifications that will far exceed those of the GeoEye-1, in two to three years. It is expected that GeoEye-2 will be able to discern objects on the ground as small as 0,25 metres in panchromatic mode.

* henk.key@reedbusiness.nl