1. Precise leveling elevation measurement: The main purpose is to obtain the subsidence range, subsidence rate and cumulative subsidence amount of the subsidence area of the stratum. The basic principle is to use the subtraction of the elevation of the leveling points obtained by the two adjacent leveling measurements to obtain each independent The amount of subsidence at the leveling point, and then according to the method of geological statistics, all the amount of subsidence at the leveling point is interpolated into a subsidence trend surface, and the maximum subsidence rate, cumulative subsidence amount and continuous subsidence area are calculated.