The BeiDou Navigation Satellite System (hereinafter referred to asthe BDS) has been independently constructed and operated by China withan eye to the needs of the country’s national security and economic andsocial development. As a space infrastructure of national significance, theBDS provides all-time, all-weather and high-accuracy positioning, navigationand timing services to global users.
In the late 20th century, China started to explore a path to develop anavigation satellite system suitable for its national conditions, and graduallyformulated a three-step strategy of development: to complete the constructionof the BDS-1 and provide services to the whole country by theend of 2000; to complete the construction of the BDS-2 and provide servicesto the Asia-Pacific region by the end of 2012; and to complete the construction of the BDS and provide services worldwide around 2020.
(1) The space segment. The BDS space segment is a hybrid navigation constellation consisting of GEO, IGSO and MEO satellites.
- BDS GEO
- BDS MEO
(2) The ground segment. The BDS ground segment consists of various ground stations, including master control stations, time synchronization/ uplink stations, and monitoring stations.
(3) The user segment. The BDS user segment consists of various kinds of BDS basic products, including chips, modules and antennae, as well as terminals, application systems and application services, which are compatible with other systems.
Currently, BDS provides 2 open service signals: B1I and B2I . The nominal frequency of B1I signal is 1561.098 MHz， and the nominal frequency of B2I signal is 1207.140 MHz.
Currently, B1I and B2I open service signals are being broadcast by the operating BDS-2 to provide open services to the Asia-Pacific region free of charge. The services cover an area extending 55°S-55°N and 70°E-150°E , with positioning accuracy less than 10 meters, velocity measurement accuracy less than 0.2 meter per second, and timing accuracy less than 50 nanoseconds.
Current Service Area