Global Positioning System is a satellite base radio positioning system that accurately provides positioning, velocity and time information to GPS device users. Continuous global positioning satellite tracking networks are being established by varieties of national and international organizations to provide basic infrastructure for space-age navigation, surveying, science, engineering, and atmospheric sensing. The system is also used for a wide range of geosciences applications. GPS signals are broadcast from a constellation of 24 or more earth orbiting satellites. As the GPS signals are derived from the atomic frequency standards on board each satellite, they are widely used as a reference for time synchronization and frequency calibration and used in any weather conditions. These systems often use satellites, receivers and the software that allow users to determine the exact geographic position. The GPS receivers convert SV signals into position, velocity, and time estimates. They have widely adopted in personal tracking, navigation and automatic vehicle located technologies etc.