Method for determining terrain following and terrain avoidance trajectories

A method for determining a terrain following and terrain avoidance trajectory for use in terrain following radars employed in guiding a moving aircraft above a predetermined terrain profile, said method comprising the steps of:

• forming a grid comprising a series of discrete terrain points corresponding to terrain above which the aircraft is to fly, each terrain point having a cost associated therewith that is function of predetermined criteria including distance of each terrain point from the aircraft, a height of each terrain point above the terrain at each distance, and attitude of the aircraft at its current position and at each terrain point, and wherein a cost is assigned to each of the discrete terrain points that is representative of the cost to get to the point based upon the predetermined criteria;
• selecting a terminal point from the series of discrete terrain points, which terminal point comprises a terrain point through which the aircraft must fly at the end of the trajectory over the terrain;
• computing a series of paths through the terrain points from a starting point at a current position of the aircraft to the selected terminal point, taking into account the aircraft's maneuvering capability and current attitude, and computing a total cost at the terminal point for each path of the series of paths, and wherein the total cost for a particular path comprises the sum of costs at the terminal point plus the respective costs of all terrain points along the particular path;
• selecting the path that has the least total cost, which selected path comprises the minimum integrated total cost over the terrain profile to arrive at the selected terminal point;
• and
• guiding the aircraft along a trajectory defined by the selected path having the minimum integrated total cost.