It is very important to calibrate the barometer in order to achieve reliable data, TwoNav provides you several ways to calibrate it:
•Manually: If you know the current altitude, enter it.
•Current GPS altitude: Takes the current altitude from the GPS by means of an algorithm that optimizes the final result.
•Current CDEM altitude: Takes the current altitude from the 3D relief map (3D relief map must be loaded).
NOTE: This option might minimize little errors of altitude data from the GPS. It also overcomes limitations of the barometric altimeter regarding atmospheric pressure and temperature, alien to altitude changes.