摘要: |
A United States Department of Defense system called NAVSTAR Global Positioning System (GPS) is revolutionizing navigation and positioning technologies. GPS is a satellite-based, radio-navigation system consisting of 24 satellites arranged in 6 orbital planes at an altitude of 20,000 km and a ground-based infrastructure that monitors and controls the satellites. Every transportation mode can benefit from GPS. On the nation's highways, GPS can provide navigation and guidance to vehicles and buses, automated voice for bus stop annunciation, and accident data collection. The rail industry can track hazardous cargo and monitor the location of entire trains on their track network to prevent collision. The most dramatic use of GPS will eventually be in guiding an aircraft from the time it takes off until the time it lands. Finally, many marine navigators use a complex system of buoys, navigational beacons, and landmarks, which can be pinpointed accurately using GPS. This article describes how GPS works, the services available and the errors associated with services, the needs and requirements of users, augmentation services, and future developments. The author reports that the advances being made today are nothing short of phenomenal. |