Altimeters based on a static pressure inputs show the altitude of the aircraft relative to sea level at the setting (QNH). They are used on any type of aircraft, whether it is an airplane, helicopter, gyroplane or airship. When choosing the Altimeter, take into account the altitude range in which the aircraft is moving, the precision of reading, the size of the instrument, as well as the units: Ft or Meters in which you want the instrument to be calibrated. An additional factor is the unit based on which you set the altimeter pressure, it can be graduated in hectopascals or in inches mercury. You should also pay attention to the certificates that a given device must meet. You will find both certified aircraft altimeters as well as their non-certified counterparts.