How is the meridian navigation satellite located?

The United States launched the world's first meridian navigation satellite, and the traditional radio navigation system was replaced. This system was mainly used by the US Navy, and was officially opened to civilian use in 1967. It consists of a navigation network consisting of four satellites. Ships all over the world can see the "meridian instrument" every 90 minutes on average, and receive its automatic signals to locate it. The positioning accuracy is about 30 ~ 40m, and each positioning takes about 8 ~ 10 minutes. Meridian navigation satellite system is a low-orbit navigation satellite, which combines the advantages of global coverage of long-range radio navigation stations and high positioning accuracy of short-range radio navigation stations. Only four satellites can provide all-weather global navigation coverage and periodic secondary (latitude and longitude) positioning capabilities.