Abstract: A method and apparatus are described for the determination of the height above a landing surface and the rate of descent to the landing surface for a fixed wing or rotary wing aircraft when the aircraft is less than about 100 feet above the landing surface. The invention relies on the time-of-flight measurement of preferably short infrared pulses that are transmitted from the sensing device and reflected back to the sensing device from the landing surface. Multiple sensors can be used for redundancy. For each sensing unit the distance is determined by a conversion of the time-of-flight information into a distance reading. The rate of descent is determined from successive distance determinations. An additional algorithm determines if the rate of descent is excessive for the distance above the landing surface and generates an alarm such as an audible or visual signal.

Abstract: A method and apparatus are described for predicting a crash and reacting thereto. Advantageously, the inventive apparatus is mounted on a vehicle and determines the time-to-impact for approaching obstacles that are within a limited distance from the host vehicle. The sensing distance from the vehicle is set by signal processing of reflected signals and rejection of all responses corresponding to a distance greater than the preset limiting value. The effect of the invention is the projection of a sensing envelope or barrier outwards from that portion of the vehicle provided with the invention. Intrusion into this envelope is sensed for appropriate action, so as to provide a warning of 10 to 40 milliseconds prior to a collision. The invention relies on time-of-flight measurement of preferably short infrared pulses to locate the obstacle. Multiple sensors are used to provide area coverage and to determine size and extent of the obstacle.