Imagine a perfect walk in the country, a few years from now - tranquillity, clean air, birdsong in the trees and hedgerows, growing crops swaying in the breeze.

Suddenly a model plane swoops overhead.

But there is no-one around manipulating radio controls. This is not a toy, but a drone on a photographic mission.

Meanwhile, hundreds of kilometres up in space, the same patch of land is being photographed by a satellite, which clearly pinpoints individual trees and animals.