Ask the master to point out the maze.

The rear intersection is a data transmission method, that is, the difference between the unknown point and the known point in front is calculated by the difference A between the known point and the front station and the difference B between the unknown point and the front station, and the height of the station is cancelled in the calculation, so the height of the front prism must be correctly input, and the height of the station instrument can be unpredictable.