navigation satellite
Quick Summary
Navigation satellites are instruments that transmit precisely controlled electromagnetic radiation, allowing users to determine their location on Earth. Early systems like the U.S. Navy's Transit in the 1960s used the Doppler effect to calculate position, though with limited accuracy.
Modern systems, such as the Global Positioning System (GPS) and Russia's GLONASS, utilize a constellation of satellites in precise orbits. These satellites carry highly accurate atomic clocks. By measuring the signal travel time from at least four satellites, a GPS receiver can calculate a user's longitude, latitude, and altitude with remarkable precision, benefiting a wide range of civilian and military applications. Other global systems include Europe's Galileo, China's Beidou, Japan's QZSS, and India's NavIC.12
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