How to locate the two stars of the Beidou satellite navigation system？

Beidou system uses two geostationary satellites (GEO) to measure the user's two-way distance, and a ground center station equipped with an electronic elevation library performs position calculation. Positioning is requested by the user terminal to the central station, and the central station calculates its position and sends the positioning information to the user. Its positioning is based on the principle of the intersection of three spheres, that is, with the known coordinates of the two satellites as the center, and the measured distance between the local satellite and the user's machine as the radius, two spheres are formed, and the user's machine must be located at the intersection of these two spheres. On the arc. The electronic elevation map library of the central station provides a non-uniform spherical surface with the center of the earth as the center and the height from the center of the sphere to the surface of the earth as the radius. Solve the intersection of the arc line and the earth's surface, and know that the target is on the north side of the equatorial plane, you can get the user's two-dimensional position.