GPS uses a principle called trilateration, which is similar to triangulation but relies on distance measurements rather than angles, to determine your exact location. It's based on the time it takes signals to travel from multiple GPS satellites to your receiver.
Here's a breakdown of how GPS trilateration works:
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Satellite Signals: GPS receivers pick up radio signals transmitted from multiple GPS satellites orbiting the Earth. These signals contain information about the satellite's position and the time the signal was sent.
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Distance Measurement: The GPS receiver calculates the distance to each satellite by measuring the time it takes for the signal to arrive and multiplying that by the speed of light (since radio waves travel at the speed of light). Think of it like this: distance = speed x time.
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Circles and Spheres: Based on the calculated distance, the receiver knows that it must be located somewhere on the surface of a sphere centered on that satellite, with a radius equal to the calculated distance. With one satellite, you could be anywhere on that sphere.
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Intersection of Spheres (Trilateration):
- With two satellites, you know you must be located somewhere along the circle where the two spheres intersect.
- With three satellites, the intersection of the three spheres narrows down your location to two possible points. One point is usually unrealistic (e.g., far out in space), so the GPS receiver discards it. This provides a 2D (latitude and longitude) position.
- With four satellites, the receiver can determine your altitude (height above sea level) in addition to your latitude and longitude, giving you a 3D position. The fourth satellite also helps correct for clock errors within the GPS receiver itself, improving accuracy.
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Location Calculation: The GPS receiver uses the information from these satellite signals to pinpoint its exact location on Earth. The more satellites the receiver can "see," the more accurate the location determination will be.
In essence, GPS uses distances from multiple satellites, whose locations are precisely known, to determine your location through the intersection of imaginary spheres.
