Overview of Global-Positioning-System

GPS is radio navigation system and it is space based and this offers on continuous navigation, reliable positioning, and timing services to civilian users, and this is freely available to all. The GPS system will provide time and location for anyone with a GPS receiver.

• Navigation satellite system: U.S department of Defense funded GPS. World-wide there are thousands of civil users of GPS, they design the system for U.S. Military and operate this GPS system. Specially coded satellite signals are provided by GPS. In a GPS receiver that can be processed, enabling the receiver to compute velocity, position and time. In three dimensions and the time offset four GPS satellite signals are used to compute positions in the receiver clock.
• Space segment: System' s space segment contains GPS satellites. Radio signals are sent by these space vehicles from space. Operational Constellation of the normal GPS contains of 24 satellites that revolve around the earth in 12 hours. Often, there are more than 24 operational satellites as they launch new ones to replace older satellites.
• Control segment: This control segment contains a system of tracking stations which placed around the world. From space vehicle, the monitor stations measure the signals and for each satellite space vehicle are incorporated into orbital models.
• User segment: The GPS user contains the user community and the GPS receiver. Space signals are converted by GPS receivers into position, time and velocity. For positioning, time dissemination, navigation and other research the GPS receivers are used. For ground vehicles, ships, aircraft, for hand carrying by individuals the navigation receivers are made.