Single-parameter terrain classification for terrain following

Abstract

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 <re and vevary with aT, the standard deviation of the terrain, and with some function of terrain bandwidth. This suggests that even for the nonlinear, nonstationary case, the ratio R — aT/lT where 1T is the terrain correlation length has a large effect on missile terrain-following performance. The parameter R is called the roughness ratio. Actual digitized terrain was processed to obtain moving estimates of R. This provides a single-parameter preliminary classification method for a variety of terrains. Simulated flights over strips of terrain confirmed that in general the missile had most difficulty where R was largest.