An integral equation approach to the propagation of low-frequency ground waves over irregular terrain 1: Ground-based terminals

Numerical calculations and theoretical developments demonstrate how topography and various approximations affect the calculated propagation of a ground wave. Extensive numerical results are presented for generic terrain types selected to illustrate salient features of solutions to the integral wave equation. Results for simple hills show that arc-length correction of the propagation path is insignificant compared with geometric effects on phase speed in predicting phase retardation. Isolated terrain features cause large local perturbations in phase arrival; far beyond the irregularity on the propagation path, effects are observable but diminish with distance.