RTC – MOD-03 – Pt.03 – What is an Altimeter

Simply put an Altimeter is just a Barometric Pressure Sensor (Barometer).

However with simple gearing, calibration, reading scale and [pressure] input, it will convert the current Barometric Pressure into a vertical distance [above (or below) the input Barometric pressure].

So with that said an Altimeter will only tell you its vertical distance above a given input Barometric pressure.

Note – From this point forward it’s important to always differentiate “Vertical Distances”, Words such as Height, Altitude, Elevation, Flight Levels, all have very specific meanings in aviation. So remember, and and get into the habit of not using them interchangeably.

Additionally, ASL (Above Sea Level) and AMSL (Above Mean Sea Level) Are also not to be used interchangeably, In essence,  AMSL should not be used in aviation.