Your location is measured using GPS (Global Positioning System) by calculating the distance between your device and several satellites orbiting the Earth.
Here's a breakdown of the process:
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Satellite Signals: Multiple GPS satellites continuously transmit signals containing their position and the time the signal was sent. These signals travel at the speed of light.
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Receiving Signals: Your GPS device (e.g., smartphone, car navigation system) receives these signals. Because the satellites are at different distances from you, the signals arrive at slightly different times.
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Time Difference Measurement: The GPS receiver precisely measures the time it took for each signal to arrive.
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Distance Calculation: Using the signal travel time and the speed of light, the GPS receiver calculates the distance to each satellite. Distance = Speed of Light * Travel Time
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Trilateration: With distance measurements from at least four satellites, your device can pinpoint your location through a process called trilateration. Imagine drawing spheres around each satellite, with the radius of each sphere representing the distance to that satellite. The point where all the spheres intersect is your location. Three satellites can give a 2D position, while a fourth is needed for altitude and increased accuracy.
- Why Four Satellites? Four satellites are required to solve for the three spatial dimensions (latitude, longitude, and altitude) and the GPS receiver's clock error. The accuracy of the GPS receiver's internal clock is generally less precise than the atomic clocks on the satellites.
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Coordinate Conversion: The calculated location is usually represented in latitude and longitude coordinates.
In summary: The GPS receiver calculates its distance from multiple satellites by measuring the time it takes for their signals to arrive. Using these distances and the known positions of the satellites, the receiver determines its location on Earth via trilateration.
