Reciprocity evaluation of the parabolic equation for propagation over a tri-linear terrain

The inaccuracies in the standard parabolic equation that are caused by violation of certain specified conditions are studied. Such violations are simulated by manipulating the slope of the middle portion of a trilinear terrain and its proximity to the transmitting antenna. The principle of reciprocity is used to provide a measure of the inaccuracy of results. For the trilinear terrain considered, it was seen that parabolic equation solutions failed for steep slopes. For slopes near the source, the sources of the implicit finite difference-Green's function method near the ground depended on the vertical extent of the mesh; a shorter mesh yielded superior results. Most of the predictions, as indicated by the reciprocity principle, were unexpectedly accurate.<>