Forward-Sensed Terrain Profile Comparison for Aircraft Geographic Orientation

The feasibility of using forward-sensed horizon or fixed-range profiles as navigation checkpoints for aircraft or missile flights above the majority of the surrounding terrain is discussed. Digital topographic data and computer simulations used for system performance analyses and parameter tradeoffs are described. Analysis results are presented for different terrain roughnesses and with and without profile errors and vehicle altitude errors. System parameters and error limits are selected to give acceptable theoretical system performance. The results indicate that horizon profiles are unsuitable at higher altitudes since the long range to the profile produces excessive profile error sensitivity. The system using fixed-range profiles is shown to be theoretically feasible. The system parameters and error limits are also used to obtain required profile sensor characteristics. The effect of profile amplitude quantization is shown and minimum required computer wordlengths are established. (Author)