How Does GPS Work?

When taking a road trip today, some sort of GPS device is essential. It may be built into the car's dashboard, or perhaps it's just an app on a smartphone. But GPS is used for more than just finding your way! Readers will be fascinated by its beginnings as a military system and its many modern uses, such as catching criminals, predicting earthquakes, and creating maps. Colorful photographs illustrate real-life examples of GPS technology, military and civilian, and informative text clearly explains the science and math concepts behind the satellites and receivers used all over the world.