An automated approach for implementing GTD to model 2-D terrain effects at microwave frequencies

The impetus for the work described arose out of the need to model absolute signal strength for a microwave landing system (MLS) operating in the presence of irregular terrain. A complete, automated approach for predicting absolute signal strength at microwave frequencies for sites involving irregular, 2-D terrain profiles is presented. The approach involves two computer models: one to convert raw terrain elevation data into a linear profile; the other to estimate path loss using the geometrical theory of diffraction. The linearization of a terrain profile is accomplished by mapping raw terrain data into a phase domain and then identifying significant terrain features from the stationary phase points as defined by Fermat's principle. Since the entire modeling process is automated, little expertise on the part of the user is required. Validation of the approach is given by comparisons of measured and modeled signal strength data for representative sites. While the model described is limited to 2-D terrain, the approach is applicable to 3-D terrain as well.