A satellite-based radio navigation system developed by the China Space Science and Technology Group. Covering only China with four GEO and one MEO satellites launched from 2000 to 2007, the system became operational in 2003. A global system based on up to 35 MEO satellites with accuracy of 10 meters is expected. Beidou is Chinese for the Big Dipper. The North Star, which has been used for centuries for navigation, is located in the Big Dipper. See GPS and GEO.