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How to Read the Indicator on an Altimeter

Altimeters measure altitude above a fixed level, such as mean sea level, or MSL. An altimeter has three indicators, which express altitude in units of 10,000, 1,000 and 100 feet, respectively. The skinniest arm -- or a roving triangle or quadrilateral shape -- indicates units of 10,000. A thick, medium-length arm indicates units of 1,000. A long arm indicates units of 100. By studying each indicator, an altimeter user can determine the altitude of his current location.

Instructions

- 1
  Note the location of the skinniest arm or roving triangle. It measures altitude in units of 10,000 feet. If it points at 2, it indicates an altitude of approximately 20,000 feet. If it is between 2 and 3, the altitude is approximately 25,000 feet.
- 2
  Observe where the thick, medium-length arm is pointing. It measures altitude in distances of 1,000 feet. If the indicator is at 5, that is roughly equivalent to 5,000 feet of altitude. If it is between 5 and 6, the measurement is approximately 5,500 feet.
- 3
  Note the location of the long, skinny arm. If it is pointing at 3, it is measuring 300 feet of altitude. If it is pointing halfway between 2 and 3, the measurement is 250 feet.
- 4
  Combine the three readings to calculate the true altitude. If the 10,000 arm is pointing at 2, the 1,000 arm at 3, and the 100 arm at 5, the altitude is 23,500 feet.

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