“…This method has the advantages of being a full-forward-wave calculation that requires relatively few approximations and accommodates lateral as well as vertical inhomogeneities in the refractive conditions. Although other propagation models are capable of accounting for horizontal refractive gradients [Cho and Wait, 1978;Wait, 1980;Pappert, 1982;Felsen, 1981], they inevitably are restricted to simplistic refractive conditions, lower frequencies, and/or certain regions of space. The parabolic equation/split-step approach, however, has been demonstrated to provide accurate predictions of normalized signal strength in complicated measured environments [Dockery and Konstanzer, 1987].…”