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09/10/1938 Easy way to measure altitude

Bell Labs demonstrated the first radio altimeter in New York. It measures the vertical distance between the aircraft and terrain. Radio altimeter was invented by American engineer Lloyd Espenschied in 1924. It took fourteen years to build a prototype adaptable for practical use on the board of an aircraft.


  • Essentials 

  • ITU definition 

  • Principle 

  • Pulse-limited altimetry 

  • Invention 

  • Military aviation applications