Global Positioning System is a space based satallite mavigating system. This system provides location and time impromation. also can be determine weather condition anywhere or near the earth. There is and unobsturucted line of sight four or more GPS satallites. It is maintained by the united States government and is freely accessible to anyone with a GPS receverAdvances technology and new dimands on the existing system have now led to efforts to modernize the GPS system and impliment the next generation of GPS 3 satellites and Next Generation Operational Control System (OCX)