Altimeter Barometer Thommen TX-22

Altimeters work on the same principle as the barometer and measure the weight of the air column. Those with the best mechanism have an accuracy of 10 m. The less precise instruments are accurate to within a range of 20 to 50 meters. Air temperature plays a role in altitude measurement. Air density has a close relation with tempera- ture. When air temperature differs from the mean temperature, one must correct the altitude: for every degree C. off, 4% of altitude must be corrected. Therefore, when there are atmospheric changes every day or hour, one must set the altimeter for a known altitude before a trip. This instrument is quite valuable to find and recognize the ground in respect of the map.