Altitude of an object above a certain set level can be measured by Altimeters. Altimeters are considered as weather instruments and are widely used for measuring altitude. The name has been derived from the word “altimetry” which indicates the measurement of altitude. Altimeters are not only used in measuring altitudes above the ground, but underwater depths are also measured by these devices.

The Altimeters mechanism is rather simple and easy. Altitudes are calculated according to the air pressure. With the increase of altitudes air pressure automatically decreases.

Altimeters are more often used for aircraft instrumentation. Pressure Altimeters also known as Barometric Altimeters are the kind of Altimeters found in most aircrafts. An aneroid barometer placed on a fixed port outside the aircraft measures the air pressure. According to the International Standard Atmosphere (ISA), the mathematical model of Altimeters is calibrated to display the air pressure directly in terms of altitude.

To measure altitude in a more direct and simple way Radar Altimeters are used. It is used in all commercial and military aircrafts. Radar Altimeters measure the height above the ground level while the aircraft prepares to land. It also indicates and warns the pilots when they are flying too low.

Other than aircraft, Altimeters are also used in several off-road vehicles helping it to navigate on rough and hilly surface. Some wrist mounted Barometric Altimeters are used by mountaineers when they are on high altitude expeditions.

Altimeters also have other scientific usages. Few satellites contain exotic dual-band Radar Altimeters so that height can be measured from spacecrafts.