A satellite-based radio navigation system developed by the China Space Science and Technology Group. Pronounced "
by-dough," there have been three independent BeiDou systems. Using four GEO satellites, BeiDou-1 started in 2000 and ended in 2012. BeiDou-2, originally known as COMPASS, began in 2007 and was designed for five GEO, 27 MEO and three IGSO (geosynchronous) satellites. Completed in 2020, BeiDou-3 uses three GEO, three IGSO and 24 MEO satellites. Accuracy is within inches.
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.