A Direct-Reading Radio-Wave-Reflection-Type Absolute Altimeter for Aeronautics

Various theoretical and experimental researches have been carried out to indicate the absolute altitude of aircraft with respect to the ground by radio-wave-reflection methods. By using a new principle, frequency modulation (FM), the following results have been obtained: 1. Completely continuous indication of altitude by a steady pointer and dial is easily accomplished and altitude variations occurring during time intervals of a few milliseconds are clearly detected. 2. Very low altitudes, less than four meters, are indicated quite easily. 3. The indication is quite linearly proportional to altitude. 4. The absolute error is zero and the relative error is less than a few per cent. 5. Altitudes in excess of 160 meters can be measured with a power consumption of only 3.9 watts. The above results show that this sounding gear is suitable for blind-landing use in aeronautics. Moreover, this gear may be applied to satisfy navigational requirements in foggy weather, to avoid the collision of ships, or to lead them into a port.