The notion of relief in images has a long history. From the 3rd century BC, Euclid, the Greek mathematician, defined the principle of 3D vision as “simultaneously receiving a different view of the same object with each eye."

Many centuries later, the invention of the stereoscope demonstrated this principle in practice, leading to the representation of relief through the simultaneous projection of two different views of the same object. This process is now successfully used with satellite imagery.

The HRS instrument on the SPOT 5 satellite goes one step further. It produces nearly instantaneous stereopairs of large areas (120 km x 60 km), at a resolution of 10 metres. The images making up stereopairs are acquired along the same orbit track, in front of and behind the satellite.

This technology paves the way for numerous applications, particularly in mapping, telecommunications and defence.

^{Last updated: May 2008}