Resumen de How gps works.

• The article presents diagrams illustrating the Global Positioning System (GPS), a radio-based worldwide navigation system comprising two dozen satellites and associated ground stations. The topics covered are intersecting spheres, timing signals, PRN codes, and synchronized clocks. Gauging the distance to a satellite requires timing how long it takes for a satellite signal to arrive at a receiver. To understand how PRN codes aid in measuring distance, consider this analogy: suppose that both the satellite and the receiver started playing the same song--the PRN code--at the same time. To synchronize the clocks in orbit with those on the earth and thus compensate for the timing error, GPS must make a fourth satellite measurement.