Who Invented the Altimeter?

Since there is more than 1 type of altimeter, credit for inventing it must go to 3 inventors, not just 1 man. The 1st altimeter was invented in France in the late 1800s. German and American inventors refined the concept in the 1920s.

First Altimeter

The 1st instrument for measuring the vertical distance or altitude of an object above a fixed point of reference was invented by Louis Paul Cailletet, a French physicist, in the 1880s. It could be used to measure surface variations of the land (hills, mountains) or the altitude of any object in relation to the land (building, aircraft). His invention was a simple barometric altimeter, also called a pressure altimeter.

Barometric Altimeters

Pressure altimeters work by measuring the difference in barometric pressure between an object in space or the top of a tall structure or mountain and the pressure at sea level. Cailletet's pressure altimeter did not give accurate readings with its single rotating needle. It was fine for measuring mountains but not accurate for aircraft. Paul Kollsman, a German inventor, changed life for aviators dramatically when he introduced the 1st accurate barometric altimeter in 1928. The accurate and reliable device was called the "Kollsman Window" and allowed pilots to navigate in mountainous terrain even in bad weather.

Radio Altimeters

Lloyd Espenscheid, an American who invented the 1st radio altimeter in 1924. It wasn't until 1937, however, that it began to be commercially produced by the Western Electric Company. In 1938, the frequency modulated (fm) radio altimeter was demonstrated by Bell Labs in New York, and the new way of measuring altitude really took off.
Radio altimeters measure absolute distance between an object, such as a weather balloon, airplane or spacecraft and the surface of the land or water beneath it. They do this by sending a radio signal to the ground and measuring the amount of time it takes to bounce back.

Other Uses

Altimeters, which can be worn on the wrist, are often used by skydivers and high-altitude climbing expeditions. Off-road vehicles are sometimes equipped with pressure altimeters to help them navigate in mountainous terrain. (In the 1930s, the Duesenberg automobile, a luxury car never intended to go off road, was equipped with an altimeter as a sort of status symbol.)

Outer Space

Sophisticated dual-band radar altimeters are installed on spacecraft such as satellites and are excellent tools for mapping the topography of the ocean floor.