The BeiDou Navigation Satellite System, also known as BDS, is a Chinese satellite navigation system. It is globally accessible and provides high-precision positioning, navigation, and timing services. The system operates with three types of satellites: Geostationary Orbit (GEO), Inclined Geosynchronous Orbit (IGSO), and Medium Earth Orbit (MEO) satellites. The system's architecture is divided into two parts: space and ground. The space segment consists of satellites in orbit, while the ground segment includes control stations, uplink stations, and user terminals. The BeiDou system utilises a unique two-way communication feature. This allows the system to provide not only positioning and navigation but also short message communication. The system's signals are transmitted at several frequencies, including B1, B2, and B3. Each frequency band has specific applications, such as B1 for open service and B2 for authorised service. The BeiDou system also uses a unique signal structure that maximises signal power and improves positioning accuracy. The system's positioning accuracy is less than 10 metres in public service, while its velocity accuracy is less than 0.2 metres per second. The BeiDou system is interoperable with other global navigation satellite systems, such as GPS, GLONASS, and Galileo. This interoperability enhances global coverage and improves positioning accuracy.
