CRANE WITH GROUND SURFACE ESTIMATION

A ground surface estimation method includes: a continuous region recognizing step for recognizing, when a difference in altitude value between a representative point of one grid and a representative point of another adjacent grid out of the plurality of grids is equal to or less than a threshold, the one grid and the other adjacent grid as a continuous region that is a region where the one grid and the other adjacent grid are continuous; and a ground surface estimation step for estimating a continuous region having the largest number of grids among the continuous regions as a ground surface.