Methods and apparatus for detecting obstacles in the flight path of an air
vehicle are described. The air vehicle utilizes a radar altimeter incorporating
a forward looking antenna and an electronic digital elevation map to provide precision
terrain aided navigation. The method comprises determining a position of the air
vehicle on the digital elevation map, selecting an area of the digital elevation
map in the flight path of the air vehicle, based at least in part on the determined
air vehicle position, and scanning the terrain representing the selected map area
with the forward looking antenna. The method also comprises combining the digital
elevation map data for the selected map area with radar return data for the scanned,
selected area and displaying the combined data to provide a representation of the
terrain and obstacles in the forward flight path of the air vehicle.
