Contact-analog headup display method and apparatus

Images are provided to a pilot in an aircraft overflying the earth by means of a helmet mounted display system. The position and attitude of the aircraft with respect to the earth and the attitude of the helmet with respect to the aircraft are monitored in order to convert a plurality of stored earth position signals into helmet coordinates. Earth points which are viewable by the pilot are displayed using symbolic images thereof such that the symbolic images coincide, from the pilot's point of view, with the actual positions of the viewable points on the earth.