Introduction - If you have any usage issues, please Google them yourself
GPS navigation systems, GPS source code for the 20th century, 70' s jointly developed by the United States armed forces a new generation of space satellite navigation and positioning system. Its main purpose is to land, sea and air to provide real-time three main areas, all-weather and global navigation services, and for intelligence gathering, nuclear explosion monitoring and emergency communications and some other military purpose is to dominate the U.S. global strategy, an important component. After more than 20 years of research laboratories at a cost of 30 billion U.S. dollars