![]() ![]() Conversely, given its precise x, y, and z coordinates, a global navigation satellite system (GNSS) receiver can use the signals emitted by the satellites to determine time with an accuracy approaching, while not equaling, that of the satellite’s atomic clock. To do so, it needs to receive and process signals from at least four satellites simultaneously, solving for x, y, and z coordinates, and time. ![]() To accurately determine its position, a GPS receiver has to synchronize its internal clock with the atomic clocks onboard the orbiting satellites. Because electromagnetic signals travel at the speed of light, a delay of just 1 microsecond would, on its own, translate to a 300-meter range error – far from the meter-level or even sub-meter-level accuracies users expect today. How on earth, you might wonder, can GPS receivers use weak electromagnetic signals emitted from distant satellites to determine its position to within just a few meters (or even centimeters)? To a large extent, it’s because they are excellent timing devices that determine their position based on the time it takes for the satellite signals to reach them from orbit.
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