Abstract: An aerial surveying method to determine ground contour utilizes a rotating laser beam to establish a horizontal reference plane to which all contour measurements are referred. A stacked-array optical sensor, suspended below the aircraft, is utilized to measure the relative height of the aircraft with respect to the reference plane. A survey track along the ground for the aircraft is determined and the position of the aircraft along the track is continuously measured. The aircraft is flown continuously along the track and repeated altitude measurements of the aircraft are continuously made. The relative height of the aircraft with respect to the laser beam, the altitude of the aircraft above the ground and the position of the aircraft along the survey track are correlated to determine the ground contours.