To avoid excessive simulation of terrain following flights, it is desirable to have a method to classify terrain with regard to its suitability for terrain following. Analytical expressions for the probability of crashing (Pc) for a terrain-following missile indicate that the variances oe and ae, of missile altitude error and error rate, respectively, have considerable effect on Pc. In general, the larger they are, the larger is Pc. Linearized studies of the missile control system interacting with stationary terrain statistics indicate that both