Global Positioning System (GPS)

Global Positioning System (GPS) is actually the formal name of the United State’s global positioning satellite constellation. There are currently 24 active satellites providing global positioning correction under the GPS system.
GPS is part of the increasingly available world stock of global positioning satellites now referred to as the global navigation satellite system, or GNSS. These other constellations include: the Wide Area Augmentation System, or WAAS, a free positioning system administered by the Federal Aviation Administration and the US Department of Transportation: GLONASS, a constellation administered by Russia.
Systems are rapidly being developed in China, India, and Japan that will increase the number of satellites available for receivers to use, which will lead to continued improvement in signal and accuracy reliability.