Target-ground Interaction - A study

Many tools examine the vehicle and evaluate its monostatic radar cross section in free space. This may be adequate for flying objects, but hardly for sea or ground vehicles. These objects must be studied in their natural surroundings, together with the background in which they are placed. For that reason one needs to have the capability to study, in the scene containing the target and the background, the radar cross section (RCS) contribution from these two parts, as well as from their interaction. In this report these, often neglected, phenomena are studied. We describe a method, based on statistical modelling, for evaluating rough surfaces (IEM, Integral Equation Method). It is also described how this method can be combined with a simple target, namely a plate represented with one facet. We also elucidate the difference between coherent and diffuse scattering. Several simulations show the properties of different types of ground, and the resulting effect when a target is placed there. The main conclusion is that the radar cross section of a target must be evaluated in its natural context, i.e., the target must be handled together with its expected surroundings. This is demonstrated through the simulations in quantitative terms, and it is seen that the effects sometimes are large.