GPS (Global Positioning System) calculates distances using a technique called trilateration, which relies on precise measurements of time and the speed of light. Here's how it works:
- Satellite Signals: GPS satellites continuously broadcast signals that contain information about the satellite's position and the time the signal was transmitted.
- Receiver Reception: A GPS receiver on Earth picks up these signals from multiple satellites. By knowing the exact time the signal was transmitted and the time it was received, the receiver can calculate the time it took for the signal to travel from the satellite to the receiver.
- Time and Distance Calculation: Since the speed of light is constant and known (approximately 299,792 kilometers per second), the receiver can use the time it took for the signal to travel to determine the distance between the satellite and the receiver. This distance is the radius of a sphere centered at the satellite.
- Trilateration: By receiving signals from at least four satellites, the GPS receiver can determine its precise location on Earth. Each satellite signal provides a distance measurement, and the intersection of these spheres (or more accurately, their surfaces) determines the receiver's position in three-dimensional space. In essence, the intersection of the surfaces of the four spheres does indeed decide the precise location of the GPS receiver. This technique, known as trilateration, is fundamental to the functioning of GPS and similar positioning systems.
In essence, GPS calculates distances by precisely measuring the time it takes for signals to travel between satellites and receivers, leveraging the constant speed of light as a reference. This allows GPS to provide accurate positioning information for navigation, mapping, and various other applications.