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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.你的手机或设备接收至少四颗以每小时14000公里速度运行的GPS卫星发来的定时信号。
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Each satellite broadcasts its exact position and the precise time the signal left—using atomic clocks accurate to nanoseconds.每颗卫星广播其精确位置及信号发出的准确时间，所用原子钟精度达纳秒级。
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Because radio signals travel at known speed, your device calculates distance to each satellite by measuring signal delay.由于无线电波传播速度已知，设备通过测量信号延迟来计算到各卫星的距离。
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With distances from three satellites, geometry narrows your location to two possible points on Earth’s surface.结合三颗卫星的距离数据，几何方法可将你的位置缩小至地球表面两个可能点。
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The fourth satellite resolves ambiguity and corrects for tiny clock errors inside your device.第四颗卫星消除位置歧义，并校正设备内部时钟的微小误差。
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Ground stations constantly monitor satellite orbits and upload correction data to maintain meter-level accuracy.地面站持续监测卫星轨道，并上传修正数据，以保持米级定位精度。
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Newer systems like Galileo and BeiDou use additional frequencies to reduce interference from buildings or trees.伽利略、北斗等新型系统采用额外频段，减少建筑物或树木造成的干扰。
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Self-driving cars combine GPS with inertial sensors and real-time maps to navigate safely in tunnels or urban canyons.自动驾驶汽车将GPS与惯性传感器和实时地图结合，实现在隧道或城市峡谷中的安全导航。