The United States GPS system was the first GNSS system available to consumers. Recently, many additional GNSS systems have gone live globally (GLONASS, QZSS, Beidou, Galileo, etc.), and many devices use multiple GNSS systems at the same time to improve coverage and accuracy.
GPS Accuracy: A well-designed GPS receiver can achieve a horizontal accuracy of 3 meters or better and vertical accuracy of 5 meters or better 95% of the time. Augmented GPS systems can provide sub-meter accuracy.
GPS Differential Correction: GPS receivers improve accuracy using two receivers because ground-based receivers can take accurate measurements of the error. As long as the stationary GPS receiver detects the same satellite signals as your GPS receiver, it can send you correction data based on its precisely surveyed location.
This augmented system broadcasts the corrected error in real-time along with the GPS signal.
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