TwoNav offers you different ways to determine the altitude value you are taking during your navigations:
•GPS: Altitude data from the GPS will be used.
•CDEM (Altitude map): Current altitude of the 3D relief map (3D relief map must be loaded).
•Barometric (manual): Values from the barometric altimeter will be used.
•Barometric (autocalibrated by GPS): Barometric altitude will be used, but the barometer will be automatically calibrated using the altitude data from the GPS by means of an algorithm that optimizes the final result.
•Barometric (autocalibrated by CDEM): Barometric altitude will be used, but the barometer will be automatically calibrated using the altitude data of the 3D relief map (3D relief map must be loaded).