STEM与日常科技·英语30篇（7）
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How GPS Knows Your Exact Location
GPS如何确定你的精确位置
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GPS receivers calculate position by measuring signal travel time from at least four orbiting satellites simultaneously.
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Each satellite transmits timestamps synchronized with atomic clocks aboard the spacecraft themselves.
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Because radio signals move at known speed—nearly 300,000 km per second—distance equals time multiplied by speed.
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Trilateration uses distances from multiple satellites to pinpoint latitude, longitude, and altitude uniquely.
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Signal delays caused by ionosphere interference are corrected using dual-frequency receivers on modern devices.
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Assisted GPS (A-GPS) downloads orbital data via cellular networks to speed up first-time location locks.
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Urban canyons weaken signals, but sensor fusion combines GPS with accelerometers and gyroscopes for smoother tracking.
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Galileo and GLONASS systems now supplement GPS, improving global coverage and redundancy for critical applications.
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Accuracy ranges from 3–5 meters for phones to under 1 cm for survey-grade equipment using ground correction.
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Behind every map pin lies precise physics, orbital mechanics, and decades of international engineering collaboration.