The features of the correlated glancing scattering of medium energy ions by the imperfect surface of a single crystal have been investigated by computer simulation It has been shown that, from the correlation of the experimental and calculated energy distributions of the scattered particles, one may determine a spatial extension of the isolated atomic steps on the single crystal surface damaged by the ion bombardment. The presence of atomic steps on the surface lead to increase of the capture probability of channeling ions in the layers under the steps and to increase of probability of their dechanneling. The obtained computer simulation results show that dechanneled ions form characteristic peaks in the angular and energy distributions of scattered particles. Character of ions movement under the step (their ranges, energy losses and dechanneling) is determined both the grazing angle and capture angle under the step.