The invention relates to a method for controlling a surface-modifying machine, wherein information on the desired condition and on the actual condition of ground to be prepared is provided and is used to derive control statements for the machine based on a comparison of the desired and the actual condition. The information on the actual condition is represented by a point cloud as a spatial distribution of discrete surface points. In order to derive control statements, at least two surface points each from the point cloud are used for every horizontal position so that non-differentiated information can be derived that for example also allow to identify various planes.