A Geometrical Model for Glide Path Measurement and Site Evaluation

A geometrical model has been developed to permit accurate and detailed characterization of the instrument landing system (ILS) null reference glide path. The model utilizes a simplified CW measuring system operating at a frequency of 9.375 GHz, which corresponds to a wavelength scaling factor of approximately 30:1. An overall accuracy of 0.01° has been demonstrated for the model facility with an "ideal" ground surface, and satisfactory agreement has been obtained between model and flight test measurements for an existing nonflat glide path site. Geometrical modelling has potential advantages over other approaches in accuracy, economy, measuring convenience, and ability to assess proposed terrain modifications.