Method for determining terrain following and terrain avoidance

Abstract

A method that enables an aircraft to determine an optimal terrain following, terrain avoidance, or threat avoidance trajectory over terrain, thereby reducing its exposure and increasing its survivability. A grid of discrete terrain points corresponding to the terrain above which the aircraft is to fly is formed. Each point has a cost that is function of predetermined criteria. A cost is assigned to each of the points that is representative of the cost to get to the point based upon the predetermined criteria. A terminal point is selected that is a point that must be flown through at the end of the trajectory over the terrain, or in order to clear an obstacle in the flight path of the aircraft. A series of paths is computed through the terrain points to a selected terminal point, taking into account the aircraft's maneuvering capability and current attitude. A total cost at the terminal point is computed for each path, and the total cost for a particular path is the sum of costs at the terminal point plus the respective costs of all terrain points along the path. The path that has the least total cost to arrive at the selected terminal point is selected. The aircraft is then guided along a trajectory defined by the selected path. The present method not only generates trajectories lower than those generated by current procedures, but also identifies regions where natural terrain masking provides cover without requiring extremely low flight, thus reducing the stress on both aircraft and pilot.