In 1978 the first satellite in the modern Navstar Global Positioning System, GPS, was launched. (The GPS's precursor, TRANSIT, was developed in the early 1960s to guide nuclear subs.) It was not until 2000, though, that President Clinton granted non-military users access to an unscrambled GPS signal.
Now, cheap, handheld GPS units can determine a person's location to within three yards. Today, there are GPS devices in cars, mobile phones, watches, and other products.