GPS has always seemed to me to be a kind of magic technology. The idea that a grid of satellites so far above my head that I cannot even see them can tell me exactly where I am and help give me directions where to go is pretty stupendous. And you do not even have to pay for the information! GPS is such a powerful technology that it is being applied to a great diversity of areas. One example is precision agriculture. For instance, if you are growing crops, they will often need water, pesticides and fertilizer. If you don’t give them enough they will have a reduced yield and if you give them too much you spend too much money and you might cause pollution. The image on the right  shows a crop that needs watering. But only the red areas are dry. So if that data is fed into a GIS databank and that is coupled to a GPS receiver on the irrigation system, the farmer will know precisely where to give water (or chemicals) so that the crop gets the right amount and there is minimal waste and runoff.