 with that trigonometry. GPS, the Global Positioning System, is just one example of trigonometry in action. Before we had GPS in the 1930s, we had the Great Triangulation of Great Britain, where all of the UK, and this has happened in countries all around the world, was very precisely mapped by covering it with a very accurate mesh of triangles, where we knew all the distances and all the angles. And we do the same thing now with GPS, just as in space.