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How Do GPS Satellites Know Your Exact Location?
GPS卫星如何精确定位你的位置？
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Your phone or device receives timing signals from at least four orbiting GPS satellites moving at 14,000 km/h.
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Each satellite broadcasts its exact position and the precise time the signal left—using atomic clocks accurate to nanoseconds.
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Because radio signals travel at known speed, your device calculates distance to each satellite by measuring signal delay.
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With distances from three satellites, geometry narrows your location to two possible points on Earth’s surface.
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The fourth satellite resolves ambiguity and corrects for tiny clock errors inside your device.
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Ground stations constantly monitor satellite orbits and upload correction data to maintain meter-level accuracy.
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Newer systems like Galileo and BeiDou use additional frequencies to reduce interference from buildings or trees.
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Self-driving cars combine GPS with inertial sensors and real-time maps to navigate safely in tunnels or urban canyons.