A Global positioning system (GPS) receiver uses signals from a set of US satellites to calculate its geographic location and establish the reference time.
GPS receivers are built into a wide variety of devices, including cell phones, navigation devices, vehicle tracking systems. Similar global systems have been established by the EU (Galileo), China (BeiDou) and Russia (Glonass); and regional systems by Japan (QZSS) and India (IRNSS); however GPS is more widely used.