ach called stochastic tional effort as for the 2D case, or even to reduce the scattering approach. Here the surface is subdivided in effort for the 2D case. The paper dealing with reduction smooth parts with different orientations. Assuming of computational efforts while using full moment a normally distributed randomness and a Gaussian au- methods [KeCu03] is using a Wiener-Hopf technique to tocorrelation coefficient, the absolute value of the gra- find analytical expressions for obtaining the look-up dient is Rayleigh distributed with a mean of (V/L) tables for the Combined Field Integral Equation (CFIE). where L is the correlation distance and oh is the root Those are combinations of relatively easy to compute mean square of the roughness. While the Kirchhoff Fresnel integrals. Only for nearly grazing incidence are formulation leads to scattering patterns that are more there some differences between the full integral equa- dependent for the coherent scattering part from the size tion methods and the analytical formulas of the trun- of the plane (in this case an plate is considered), cated half planes. For a practical case of a German the stochastic scattering approach does show mostly the terrain profile computed at 970 MHz, virtually no dif- scattering due to the roughness, which may be much ference between both methods is seen, even with plate larger than the classical stationary phase assumption in lengths of about 30%. Another paper [BrCu01] is in- the Kirchhoff case. For this case, with a correlation troducing an integro-differential equation including the distance of 42 and a roughness of 0.35A, the significant gradients of the surface transverse to the direction of scattering areas are reduced considerably with respect to propagation. By approximating the phase on the trans- the Kirchhoff case, which shows a full diffraction pat- verse parts of the surface by a second order polynomial, tern. All values are computed at a far-field distance of the 2D Magnetic Field Integral Equation (MFIE) for 20002 from 